Virion protein involved in the primary attachment to host flagellar receptor. This attachment allows the prokaryotic virus to move along the host flagellum to find its entry receptor for viral genome penetration. Some prokaryotic viruses such as bacteriophages Chi or PV22 specifically interact with their host's flagellum, move toward the base of the flagellum to come in contact with the host cytoplasmic membrane and deliver the viral genome into the host cytoplasm
Virion protein involved in the interaction with bacterial pili, which are retractile filaments that protrude from bacteria with 2 membranes (Gram-negative bacteria). Binding to the pilus is followed by retraction of the pilus, which translocates the bound virion to the bacterial surface and allows subsequent viral genome penetration into host cytoplasm. Bacteriophages M13, f1, fd, R17, Qbeta, Pf1, Pf3, phiKMV or phi6 for example utilize the host cell pilus as an attachment structure
Protein that belongs to the cyclin family or that contains a cyclin box-like domain. Cyclins are regulatory subunits of the cyclin- dependent protein kinases. They form kinase holoenzymes, with distinct biochemical characteristics and nonredundant biological functions, which mediate phosphorylation of cellular proteins, including key cell cycle regulatory molecules. In this way, the kinase holoenzymes promote the transit of cells through the division cycle. Cyclins accumulate during interphase of eukaryotic cell cycle and are destroyed at the end of mitosis
Protein which is a component of a voltage-gated channel. Voltage-gated ion channels are responsible for the electrical activity in a variety of cell types. They probably exist in all life forms
Toxin which induces the leakage of blood components into tissues by damaging endothelial cells or disturbing endothelial cell interactions with the basement membrane. Hemorrhagic toxins are mostly found in snake venoms
Protein involved in the synthesis of lipopolysaccharides (LPS), the main constituents of the outer cell wall of Gram-negative bacteria LPS are composed of lipid molecules joined to polysaccharides and are highly immunogenic
Virion protein involved in breaking down host cell lipopolysaccharides (LPS) to reach the cytoplasmic membrane of prokaryotes with 2 membranes. Many prokaryotic viruses carry glycanase or deacetylase activities to digest host LPS
Protein sequenced from a hybridoma, an artificially produced hybrid cell line created by fusion of a lymphocyte and a myeloma cell. These cells can multiply indefinitely in culture and produce monoclonal antibodies
Protein which inhibits signal transduction, the process by which extracellular signals induce intracellular responses. Usually a hormone or neurotransmitter binds to a cell surface receptor which is coupled to a second messenger system, such as that involving cAMP, or to an ion channel. The final downstream consequence of signal transduction is a change in the cell's function, such as a modification in glucose uptake or in cell division. Such a change may be the result of an activation or an inhibition event
Viral protein involved in the evasion of host adaptive immune response by inhibiting the presentation of loaded MHC class II molecules at the cell surface. MHC class II molecules are found only on a few specialized cells termed professional antigen-presenting cells (APCs) This group includes macrophages, dendritic cells and B-cells. Many viruses 'intercept' the loaded MHC class II molecules and retain them in the endoplasmic reticulum or target them to degradation in order to prevent presentation of the peptides at the cell surface
Cell membrane glycoprotein forming a channel in a biological membrane selectively permeable to calcium ions. Calcium is essential for a variety of bodily functions, such as neurotransmission, muscle contraction and proper heart function
Protein which participates in the biochemical reactions where cholesterol is involved, including transport. Cholesterol is the major sterol of higher animals and an important component of cell membranes, especially of the plasma membrane
Protein that is involved in phagocytosis or that renders the organism resistant to phagocytosis, the process by which a cell is engulfed and broken down by another for purposes of defense or sustenance
Viral Protein involved in the synthesis of messenger RNAs. The process can occur in the host cell nucleus or cytoplasm, and the genomic template can be viral DNA or RNA, single- or double-stranded
Protein involved in the synthesis of diaminopimelate, the ionic form of the amino acid diaminopimelic acid (DAP) which is found in the murein peptidoglycans of bacterial cell walls. Diaminopimelic acid is synthesised from aspartate
Protein involved in the synthesis of neurotransmitters. The proteins are released by the axon terminal in response to an electrical impulse and travel across the synapse to either excite or inhibit the target cell
Protein involved in the breakdown of neurotransmitters. The proteins are released by the axon terminal in response to an electrical impulse and travel across the synapse to either excite or inhibit the target cell
Protein involved in the transport of neurotransmitters. The proteins are released by the axon terminal in response to an electrical impulse and travel across the synapse to either excite or inhibit the target cell
Protein involved in the synthesis of teichoic acid, a polymer of mainly glycerol phosphate or ribitol phosphate substituted extensively with amino acids and/or sugars. Teichoic acid occurs in the cell wall of Gram-positive bacteria
Protein involved in the exchange of anions across a membrane. Anion exchange is a cellular transport function which contributes to the regulation of cell pH and volume by a functionally related anion exchanger protein family
Protein which is found in the part of the plant which is external to the living protoplast, ie the cell wall, the intercellular space and the lumina of dead cells such as xylem vessels and tracheids
Protein encoded by an oncogene, which promotes cell transformation Examples include viral homologs of cellular proto-oncogenes such as the transcription factors v-myc and v-jun, the growth factor v-fgr, the regulatory GTPase v-ras, and papillomavirus protein E6
Protein which is a component or which is associated with the cytoskeleton, a dynamic three-dimensional filamentous structure in the cytoplasm. The cytoskeleton is both a muscle and a skeleton, and its roles include maintenance of cell shape, cell movement (in eukaryotes), cytokinesis, and the organization of the organelles within the cell. This includes the major components of cytoskeleton; microfilaments (actin-like proteins), microtubules (tubulin-like proteins) and intermediate filaments (mostly in eukaryotes) and prokaryotic MinD-ParA proteins. Originally not thought to exist in prokaryotes, but now known to have the same functions as in eukyaryotes
Protein involved in plant defense, either as part of preexisting, developmentally regulated defense barriers (such as thionins, defensins or hydroxyproline-rich glycoproteins fortifying the cell wall) or as components of the defense responses induced upon pathogen infection during hypersensitive cell death (HR), local acquired resistance (LAR) or systemic acquired resistance (SAR). This includes proteins involved in various pathways, such as the gene-for-gene resistance, the salicylic acid (SA)-dependant resistance, the jasmonate (JA) and/or ethylene (ET)-dependant resistance and the induced systemic resistance (ISR), as well as the final products of those pathways such as the pathogenesis-related proteins
Viral protein that is expressed by a prokaryotic virus, integrated or not, to help protect the host cell from superinfection, a process by which a cell that has previously been infected by one virus subsequently gets coinfected with a different strain of the virus, or another virus. Superinfection exclusion can be achieved for example by expressing viral enzymes that alter a portion of a surface receptor thereby blocking entry of incoming viruses with this receptor specificity. Exclusion protein can also target and block the ejection and/or DNA delivery by new incoming phages
Protein involved in the phosphotransferase system, the major carbohydrate transport system in bacteria. This phosphotransferase system catalyzes the transfer of the phosphoryl group from phosphoenolpyruvate to incoming sugar substrates concomitant with their translocation across the cell membrane
Viral protein involved in the extrusion of viral particles from the host prokaryotic cell. Extrusion is a concerted mechanism of assembly and secretion used by filamentous phages to release mature viral particles without inducing host cell lysis
Protein which is membrane-bound or membrane-associated with the host membrane, a lipid bilayer which surrounds host enclosed spaces and compartments. This selectively permeable structure is essential for effective separation of a host cell or organelle from its surroundings
Viral protein involved in the modulation of host cell cycle progression by dysregulating the G1/S transition. Some viruses benefit from an arrest in G1 to S phase transition, while others force through S phase to favor their own replication
Viral protein involved in the modulation of host cell apoptosis by acting different steps of the process. Several viruses encode proteins that inhibit apoptosis while other viruses use apoptosis to their advantage to suppress immune response or to disseminate
Antibody produced by a single clone of B cells and thus consisting of a population of identical antibody molecules all specicfic for a single antigenic determinant. They are produced from cultured hybridoma cell lines for research and commercial purposes
Viral protein involved in the modulation of host cell cycle by inhibiting the G2/M transition. A variety of viruses have been associated with G2/M arrest, including some DNA viruses, some RNA viruses and retroviruses but the mechanisms by which arrest is achieved greatly differs between those viruses
Protein located in the space between the inner membrane and the outer membrane (cell wall) of Gram negative bacteria and some eukaryotic algae. Also used for proteins located in the region between the plasma membrane and the cell wall in fungi
Protein involved in the complement alternate pathway which activates the proteins of the complement system. This pathway can be activated by IgA immune complexes, but also by bacterial endotoxins, polysaccharides and cell walls, without participation of an antigen- antibody reaction
Protein involved in the synthesis of alginate. Alginate is an exopolysaccharide in the cell walls of brown algae and in the capsular material of certain strains of Pseudomonas and Azotobacter, in which it provides a protective barrier against host immune defenses and antibiotics
Protein involved in chromosome partition, the process by which newly replicated plasmids and chromosomes are actively segregated prior to cell division. E.g., par and soj which contribute to efficient chromosome partitioning by serving functions analogous to centromeres (i.e. pairing or positioning of sister chromosomes)
Protein belonging to the set of cell surface antigens found chiefly, but not solely, on blood cells. More than fifteen different blood group systems are recognised in humans. In most cases the antigenic determinant resides in the carbohydrate chains of membrane glycoproteins or glycolipids
Viral protein that counteracts the translation shutoff set up by the bacterial host in order to inhibit viral replication. This antiviral defense system alters a crucial cellular process thereby blocking virus multiplication and ending up with host dormancy or even cell death. For example, some E.coli strains infected by bacteriophage T4 activate an anticodon nuclease which causes depletion of tRNA(Lys) and, consequently, abolishes T4 protein synthesis and causes cell death. However, this effect is counteracted by the repair of tRNA(Lys) in consecutive reactions catalyzed by the viral enzymes polynucleotide kinase and RNA ligase. The ToxIN system functions as a toxin-antitoxin (TA) tandem which is used as a antiviral defense mechanism
Receptors which transduce extracellular signals across the cell membrane. At the external side they receive a ligand (a photon in case of opsins), and at the cytosolic side they activate a guanine nucleotide-binding (G) protein. These receptors are hydrophobic proteins that cross the membrane seven times
Protein with at least one TPR repeat. The TPR repeat of typically 34 amino acids was first described in the yeast cell division control protein 23 (CDC23) and later found to occur in a large number of proteins. A function for this repeat seems to be protein-protein interaction
Protein expressed in the merozoite stage of sporozoite parasites, an invasive stage in the life cycle produced by schizogony or asexual reproduction in which the nucleus of a cell undergoes division several times. This results in a multinucleate schizont which subsequently gives rise to a number of uninucleate cells called merozoites
Protein involved in the response to stress, a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of some stressful conditions. The stress is usually, but not necessarily, exogenous (e.g. temperature, humidity, ionizing radiation, hypertonicity, amino acid deprivation)
Protein present in the glyoxysome, a membrane-surrounded plant cell organelle, especially found in germinating seeds, and involved in the breakdown and conversion of fatty acids to acetyl-CoA for the glyoxylate bypass. Since it is also rich in catalase, the glyoxysome may be related to the microbodies or peroxisomes or derived from them
Protein involved in the synthesis of brassinosteroids, a class of steroid plant hormones. Brassinosteroids are involved in numerous plant processes, such as cell expansion and elongation (in association with auxin), vascular differentiation, pollen elongation and pollen tube formation and protection to plants during chilling and drought stress. Brassinolide is the first isolated brassinosteroid
Protein involved in the Notch signaling, a signaling pathway involved in cell-cell communications that regulates a broad spectrum of cell- fate determinations. Notch proteins are transmembrane receptors, which are cleaved by the gamma-secretase complex upon activation and released from the cell membrane and turn into transcriptional activators after their association with SU(H) proteins
Protein found in or associated with a cilium, a cell surface projection found at the surface of a large proportion of eukaryotic cells. The two basic types of cilia, motile (alternatively named flagella) and non-motile, collectively perform a wide variety of functions broadly encompassing cell/fluid movement and sensory perception. Their most prominent structural component is the axoneme which consists of nine doublet microtubules, with all motile cilia - except those at the embryonic node - containing an additional central pair of microtubules. The axonemal microtubules of all cilia nucleate and extend from a basal body, a centriolar structure most often composed of a radial array of nine triplet microtubules. In most cells, basal bodies associate with cell membranes and cilia are assembled as 'extracellular' membrane-enclosed compartments
Protein involved in adaptive immunity. Vertebrates can develop a broad and almost infinite repertoire of antigen-specific receptors, which allows vertebrates to recognize almost any potential pathogen or toxin and to mount antigen-specific responses to it. Two types of adaptive immunity systems have evolved in vertebrates in order to generate immune receptor diversity. The jawed vertebrates strategy uses the V(D)JC recombination to achieve combinatorial diversity of immunoglobulin-based B cell receptors and T cell receptors. The jawless vertebrate strategy uses the somatic rearrangements of variable leucine-rich cassettes in the variable lymphocyte receptors (VLRs). The hallmarks of an adaptive immune system is the production of antigen-specific recognition receptor by somatic gene rearrangement. The long life of some antigen-primed cytotoxic lymphocytes and plasma cells provide protective memory to prevent reinvasion
Protein involved in the intracellular transport of proteins from one location to another. All proteins (except the ones synthesized in mitochondria and plastids) are synthesized on ribosomes in the cytosol. Most proteins remain in the cytosol. Proteins with a signal sequence either become plasma membrane components or are exported from the cell of origin
Viral protein involved in the activation of host cell apoptosis by acting on host caspases. While many viruses encode protein that inhibit apoptosis, viruses can also use apoptosis to their advantage to suppress immune response or to disseminate. Therefore, some viral proteins are able to cleave or activate caspases in order to promote apoptosis
Protein involved in gastrulation, a stage in early embryogenesis in which cell movements result in a massive reorganization of the embryo from an initially unstructured group of cells, the blastula, into a multi-layered organism. During gastrulation, the primary germ layers (endoderm, mesoderm, and ectoderm) are formed and organized in their proper locations for further development
Protein with at least one sialic acid. The term "sialic acid" refers to the group of sugars including neuraminic acid and its derivatives, not to a specific sugar. They are widely distributed in bacteria and animal tissue as components of polysaccharides, glycoproteins and glycolipids. They are typically the terminal residues on cell surface oligosaccharides
Protein which functions as a hormone, a biochemical substance secreted by specialized cells that affects the metabolism or behavior of other cells which possess functional receptors for the hormone. Hormones may be hydrophilic, like insulin, in which case the receptors are on the cell surface, or lipophilic, like the steroids, where the receptor can be intracellular
Protein involved in the transport of ions. Such proteins are usually transmembrane and mediate a movement of ions across cell membranes Transport may be passive (facilitated diffusion; down the electrochemical gradient), or active (against the electrochemical gradient). Active transport requires energy which may come from light, oxidation reactions, ATP hydrolysis, or cotransport of other ions or molecules
Protein encoded by the apicoplast genome or protein located in the apicoplast, a plastid found in some apicomplexan parasites which is a non-photosynthetic plastid relict. This organelle contains ring-like DNA of about 35 Kb as a third type of cell genome. Apicoplasts do not contain thylakoids; it is not yet clear if they contain internal membranes
Protein found in a fimbrium or pilus. A fimbrium or pilus is a hair- like, non-flagellar, polymeric filamentous appendage that extend from the bacterial or archaeal cell surface, such as type 1 pili, P-pili, type IV pili or curli. Pili perform a variety of functions, including surface adhesion, motility, cell-cell interactions, biofilm formation, conjugation, DNA uptake, and twitching motility
Viral protein sharing sequence similarity with host BCL2 protein Cellular BCL2 family members are divided in two groups, some having anti-apoptotic activity (such as BCL2 itself) while others have pro- apoptotic function (such as BAX). If the level of proapoptotic members are higher than inhibitors, then the cell undergoes apoptosis. So far, all viral homologues display anti-apoptotic activity
Protein involved in meiotic processes or in regulation of meiosis Meiosis is the nuclear division which results in the daughter nuclei each containing half the number of chromosomes of the parent. It comprises two distinct nuclear divisions, the first and second meiotic divisions (which may be separated by cell division), the actual reduction in chromosome number takes place during the first division
Protein involved in the movement of sodium ions across energy- transducing cell membranes. Primary active sodium transport is coupled to an energy-yielding chemical reaction such as ATP hydrolysis Secondary active transport utilizes the voltage and ion gradients produced by the primary transport to drive the cotransport of other ions or molecules. These may be transported in the same (symport) or opposite (antiport) direction
Protein which is involved in the formation, organization, maintenance and degradation of the cilium, a cell surface projection found at the surface of a large proportion of eukaryotic. Their most prominent structural component is the axoneme which consists of nine doublet microtubules, with all motile cilia - except those at the embryonic node - containing an additional central pair of microtubules
Virion exolysin involved in breaking down host cell peptidoglycans (e.g. murein, pseudomurein) to reach the host cytoplasmic membrane during virus entry. Exolysins are usually part of the tail or the base plate of prokaryotic viruses. Exolysins can display various enzymatic activities such as lysozyme, transglycosylase, muramidase or even protease activity. Murein hydrolases for example are widespread in bacteriophages infecting Gram-positive or Gram-negative bacteria
Protein which binds hyaluronic acic, an acidic glycosaminoglycan which consists of repeating units of the disaccharide composed of D- glucuronic acid and N-acetyl-D-glucosamine. This linear polymer is present in cell coats and in the extracellular ground substance of the connective tissues of vertebrates; it also occurs in the synovial fluid in joints and in the vitreous humor of the eye
Viral protein involved in the evasion of the interferon pathway by inhibiting interferon receptors. Interferon signaling exerts antiviral effects through cell surface receptors termed interferon receptors. In response to binding of extracellular interferons, they activate the JAK/STAT pathway causing transcriptional activation of IFN-regulated genes. To avoid this antiviral response, several viruses target the interferon receptors and send them to degradation via the proteasome
Protein involved in quorum sensing (QS). QS is a phenomenon whereby the accumulation of signaling molecules enables a single cell to sense the number of bacteria (cell density). The bacterial reponse to QS includes adaptation to availability of nutrients, defence against other microorganisms which may compete for the same nutrients and the avoidance of toxic compounds potentially dangerous for the bacteria
Viral protein sharing sequence homology with cellular cyclins. Most viral cyclin homologues are closely related in sequence to the cellular D-type cyclins, which are implicated in regulating the transit of cells from G1 into S and are thought to operate via the inactivation of the retinoblastoma tumour suppressor protein
Protein found in the cytoplasm, the content of a cell within the plasma membrane and, in eukaryotics cells, surrounding the nucleus This three-dimensional, jelly-like lattice interconnects and supports the other solid structures. The cytosol (the soluble portion of the cytoplasm outside the organelles) is mostly composed of water and many low molecular weight compounds. In eukaryotes, the cytoplasm also contains a network of cytoplasmic filaments (cytoskeleton)
Protein present in the flagellum, a long whip-like or feathery structure which propels the cell through a liquid medium. This motile cilium is produced by unicellular eukaryotes and by the motile male gametes of many eukaryotic organisms. The flagella commonly have a characteristic axial '9+2' microtubular array (axoneme) and bends are generated along the length of the flagellum by restricted sliding of the nine outer doublets
Viral protein involved in virus internalization into the host cell via endocytic pathways that involve neither clathrin nor caveolins. These pathways can be further defined by their dependency on various molecules such as cholesterol, DNM2/Dynamin-2, small GTPases or tyrosine kinase and possibly involve non-caveolar lipid rafts Clathrin- and caveolin-independent pathways are used by viruses including poliovirus, human rhinovirus 14, lymphocytic choriomeningitis virus, murine norovirus-1 and SV40
Viral protein involved in the inhibition of host autophagy. Autophagy is a major intracellular pathway in the delivery of cytoplasmic material to lysosomes for degradation. It is also essential for the removal of pathogenic protein aggregates from the cell during infection. Several viruses including influenza and HIV-1 block autophagosome maturation by interacting with and inhibiting host Beclin-1, an essential protein playing a central role in autophagy
Protein associated with the kinetoplast DNA (kDNA), the mitochondrial DNA of trypanosomatid protozoa. kDNA is a massive network, composed of thousands of topologically interlocked DNA circles. Each cell contains one network condensed into a disk-shaped structure within the matrix of its single mitochondrion. The kDNA circles are of two types, maxicircles present in a few dozen copies and minicircles present in several thousand copies
Component of the membrane attack complex which groups the complement plasma glycoproteins C5b, C6, C7, C8 and polymeric C9 on biological membranes. The complex forms transmembrane channels which displace lipid molecules and other constituents, thus disrupting the phospholipid bilayer of target cells leading to cell lysis by osmotic leakage. The formation of the membrane attack complex is the terminal step in the complement cascade
Viral protein involved in the modulation of host NK-cell activity Natural killer (NK) cells are critical in defense against viral infections, since they provide host protection by releasing cytokines such as IFN-gamma or by direct lysis of infected targets. Therefore, during viral infections, viruses and NK cells are in a constant battle and many viruses have developed a variety of strategies to modulate NK cell activity
Enzyme which catalyzes the transfer of the terminal phosphate of ATP to a specific tyrosine residue on its target protein. Many of these kinases play significant roles in development and cell division Tyrosine-protein kinases can be divided into two subfamilies: receptor tyrosine kinases, which have an intracellular tyrosine kinase domain, a transmembrane domain and an extracellular ligand-binding domain; and non-receptor (cytoplasmic) tyrosine kinases, which are soluble, cytoplasmic kinases
Viral protein involved in the evasion of host adaptive immune response by inhibiting the tapasin/TAPBP protein. tapasin/TAPBP is a type I transmembrane protein essential for the optimal expression of stable MHC class I molecules on host cell surface. Its helps the MHC class I molecules to remain in a peptide receptive state, avoiding irreversible denaturation. Several retroviruses and DNA viruses encode proteins interacting with tapasin/TAPBP and inhibiting its activity
Protein whose normal cellular gene can be converted into a cancer- promoting oncogene by activating mutations, chromosomal translocation or DNA amplification. Once activated a proto-oncogene can promote cell transformation in culture or tumorigenesis in animals. Examples include the regulatory GTPase HRAS, which is commonly activated by dominant gain of function point mutations, and the transcription factor MYC, which can be activated by both chromosomal amplification and chromosomal translocation
Viral or cellular protein involved in a host-virus interaction Viruses interact with many cellular pathways to achieve their replication cycle. Entry into the host cell, transport to the viral replication sites or viral exit from the host cell are all steps that require specific interactions between the virus and its host Additionally, the evasion from the host immune response requires a lot of viral proteins to associate with and inhibit cellular proteins with antiviral functions
Protein of the integrin family of cell surface heterodimeric receptors that mediates dynamic cell-to-cell as well as cell-to-matrix adhesion Integrins function as mechanochemical sensors and transducers able to change rapidly and reversibly their adhesive functions by modulating their ligand-binding affinity. Each subunit has a large N-terminal extracellular domain followed by a transmembrane domain and a short C- terminal cytoplasmic region. Some subclasses of integrins share a common beta chain while having different alpha chains
Viral protein involved in the evasion of type I and III interferon pathways by inhibiting STAT2 protein. Upon viral infection, STAT2 is activated by IFN-alpha/beta or IFN-lambda that bind to specific cell surface receptors. In turn, IFN-alpha/beta (or IFN-lambda) induces heterodimerization of STAT1 and STAT2 by phosphorylation, leading to STAT2 nuclear localization and subsequent induction of IFN-stimulated genes. Many viruses interfere with STAT2 activation, often by preventing STAT2 phosphorylation and nuclear localization
Viral protein involved in the evasion of host immune defense by inhibiting the BST2/tetherin protein. BST2/tetherin is an alpha interferon-inducible cellular factor that impairs the release of many enveloped viruses, including human immunodeficiency virus type 1 (HIV- 1), HIV-2, as well as other retroviruses. Several viruses manage to circumvent the antiviral activity of BST2/tetherin either by sending BST2/tetherin to degradation (HIV-1) or by lowering the presence of BST2 on cell surfaces (HIV-2)
Protein located in or on the magnetosome, a membrane-bound bacterial organelle that envelops crystals of magnetic iron minerals in magnetotactic bacteria. Magnetosomes form linear chains that align along the cellular motility axis at midcell and function in bacterial navigation along the Earth's magnetic field. They are formed by invagination of the cell inner membrane; in some species they remain connected to the inner membrane, in others they pinch off to form independent intracellular vesicles
Small secreted proteins from higher eukaryotes which affect the growth, division and functions of other cells, e.g. interleukins, lymphokines, TNF and interferons. Generally, growth factors are not classified as cytokines, though TGF is an exception. Chemokines are a subset of cytokines. They differ from classical hormones in that they are produced by a number of tissues or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner
Viral protein involved in the evasion of host innate defense by inhibiting the interferon signaling pathway leading to the production of interferon-induced genes. Interferons bind to the IFN receptors (IFNAR) on the cell surface and activate Jak/Tyk kinases. These kinases phosphorylate STAT1 and STAT2 that translocate to the nucleus and induce the expression of interferon stimulated genes (ISGs). Many viruses interact with components of this pathway to prevent expression of ISGs and inhibit the host immune response
Viral protein involved in the evasion of the type I, II and III interferon pathways by inhibiting the STAT1 protein. Upon viral infection, STAT1 is activated by IFN-gamma, IFN-alpha/beta, or IFN- lambda that bind to specific cell surface receptors. While IFN-gamma induces STAT1 homodimerization, IFN-alpha/beta and IFN-lambda stimulate heterodimerization of STAT1 and STAT2, both leading to STAT1 nuclear localization and subsequent induction of IFN-stimulated genes Many viruses interfere with STAT1 activation, often by preventing STAT1 phosphorylation and nuclear localization
Viral protein that allows the active transport of viral components and assembled, complete particles along microtubules toward the cell periphery during virus egress. This transport, which usually involves interaction with motor proteins like kinesin or polymerization/depolymerization reactions as a driving force, is mostly used by viruses that replicate their genome near or in the nucleus and allows newly assembled viral progeny to reach the plasma membrane. Herpes simplex virus for example is transported anterogradely along the axon
Protein synthesized or activated in the cell in response to viral infection, or protein with specific antiviral activity within the cell. Eukaryotic cells have an innate immune mechanism to fight viral infection, which is activated through the interferon signaling pathway or through dsRNA detection in the cytoplasm. It leads to the establishment of an antiviral cell state, which prevents virus replication or induces apoptosis. Most viruses have developed specific proteins to prevent the establishment of an antiviral state. About half of all bacteria and most archaea have a CRISPR (clustered regularly interspersed short plaindromic repeats) system of adaptive immunity to exogenous DNA. CRISPRs clusters are tandem arrays of alternating repeats and spacers, where the spacers in some cases are homologous to sequences from virus and plasmid genomes. The CRISPR arrays are transcribed, processed and in some way aid in detection and resistance to foreign DNA. In at least a few bacteria (E.coli, S.epidermidis) it seems DNA is the target, whereas in Pyrococcus furiosis it seems the CRISPR system targets RNA
Protein involved in the brassinosteroid (BR) signaling pathway (e.g transport and signal transduction) that regulates many aspects of plant growth and development including cell expansion and elongation (in association with auxin), vascular differentiation and pollen elongation and pollen tube formation. Also involved in plants protection during chilling and drought stress. BRs are polyhydroxysteroid phytohormones and over 70 BR compounds have been isolated in plants. Brassinolide was the first BR isolated from Brassica napus and remains one of the most active BR
Viral protein involved in the activation of host autophagy. Autophagy is a major intracellular pathway in the delivery of cytoplasmic material to lysosomes for degradation. It is also essential for the removal of pathogenic protein aggregates from the cell during infection. Although autophagy is clearly important for antiviral immune response, it can also be activated by viruses and serves as platform for viral replication. Some viruses such as poliovirus, use the autophagic pathway as a nonlytic mechanism for viral release
Protein which, if defective, causes familial hemophagocytic lymphohistiocytosis. FHL is a genetically heterogeneous, autosomal recessive disorder characterized by immune dysregulation with hypercytokinemia and defective natural killer cell function. The clinical features of the disease include fever, hepatosplenomegaly, cytopenia, hypertriglyceridemia, hypofibrinogenemia, and neurological abnormalities ranging from irritability and hypotonia to seizures, cranial nerve deficits and ataxia. Hemophagocytosis is a prominent feature of the disease, and non-malignant infiltration of macrophages and activated T lymphocytes in lymph nodes, spleen and other organs is also found
Protein component of gap junctions which are specialized regions of the plasma membrane formed by a cluster of channels allowing small molecules to diffuse from the cytosol of one cell to that of an adjacent cell. A current model of the gap junction consists of a cluster of gap-junction channels. Both membranes contain connexon hemichannels, composed of a hexamer of an integral membrane protein which is often referred to as connexin. The junction of two adjacent connexons forms a gap-junction channel
A globular structural motif found in many proteins of the immune system, including immunoglobulins (Igs), T cell receptors (TCRs) and major histocompatibility complex (MHC) molecules. Ig domains are approximately 110 amino acid residues in length, include an internal disulfide bond, and contain two layers of beta-pleated sheets, each layer composed of three to five strands of antiparallel polypeptide chains. Ig domains are classified as V-like or C-like on the basis of closest homology to either Ig V or C domains
Viral protein involved in the evasion of host adaptive immune response by inhibiting the TAP complex. Transporter associated with antigen (TAP), composed of two subunits TAP1 and TAP2, is required for the translocation of peptides into the ER, where they are loaded onto MHC class I. Thereafter, the viral peptides are presented to cytotoxic T lymphocytes at the cell surface and trigger immune response. The loading of peptide on MHC by TAP is targeted by several viruses including herpesviruses and retroviruses
Protein phosphatase-1 (PP1) is a member of the Serine/Threonine phosphatases. The enzyme regulates many important physiological processes, including gene transcription, translation, metabolism, cell growth and division. Different viruses including asfivirus, herpes simplex virus or papillomavirus interact with and modulate PPP1 phosphatase activity to dephosphorylate specific cellular substrates including EIF2S1. Upon viral infection, the host PKR/EIF2AK2 triggers the phosphorylation of EIF2S1 leading to a complete translational shut-off. By dephosphroylating EIF2S1 with PPP1CA, viruses manage to circumvent this antiviral response and prevent translational shut-off
Viral protein involved in the entry of the virion into the host cytoplasm via the host pili, which are retractile filaments that protrude from bacteria with 2 membranes (Gram-negative bacteria) Entry of bound prokaryotic viruses such as filamentous viruses is achieved through the retraction of host pilus and translocation of the virion through the basis of the pilus to reach the host cytoplasm Examples of bacteriophages which utilize the host cell pilus to penetrate into host cytoplasm are bacteriophages M13, f1, fd, R17
Protein which, if defective, causes congenital absolute erythrocytosis, a disorder characterized by expansion of the erythrocyte compartment in the peripheral blood. Total red cell mass is increased in the absence of a reduction of plasma volume Erythrocytoses are usually divided into primary and secondary forms Primary erythrocytoses are due to defects in the erythroid progenitors and are characterized by low erythropoietin levels. Secondary erythrocytoses can be due to defects in hypoxia sensing, or to conditions that cause low tissue oxygen tension with consequent increase in erythropoietin secretion
Protein that is covalently anchored to the peptidoglycan of a cell wall envelope. In Gram-positive bacteria, binding proceeds through a transpeptidation mechanism which requires a C-terminal sorting signal with a conserved LPXTG or LPXAG motif; an amide bond is created between the alpha-carboxyl group of the conserved threonine, alternatively alanine, and the amino group of peptidoglycan cross- bridges. In Gram-negative bacteria, binding proceeds through the formation of an isopeptide bond between the epsilon-amino group of a lysine and the alpha-carboxyl group of a peptidoglycan diaminopimelic acid
Viral protein expressed primarily to establish and maintain latency, the part of the viral life cycle during which a virus lies dormant (latent) within a cell. This part of the virus life cycle is called the lysogenic part in prokaryotic viruses. During latency, the viral genome can either exist as a provirus integrated in the host genome (proviral latency) or as a linear or circular plasmid in the host cell (episomal latency). The virus does not replicate, but is passively duplicated when the host divides
Protein involved in a system responding to environmental changes characterized usually by a sensor kinase in the cell membrane that phosphorylates itself in response to a signal and a response regulator to which the phosphoryl group is transferred. The responder is typically a DNA-binding protein that regulates transcription. Several of these systems are quite complex, involving many proteins in a signaling cascade or contributing to several responses simultaneously They are involved in a variety processes such as chemotaxis, osmoregulation, magnesium transport, pH tolerance, sporulation, or response of virulent species to host cell's environments
Protein which is implicated in heterocyst formation. A heterocyst is a differentiated cyanobacterial cell that carries out nitrogen fixation The heterocysts function as the sites for nitrogen fixation under aerobic conditions. They are formed in response to a lack of fixed nitrogen (NH4 or NO3). The morphological differentiation is accompanied by biochemical alterations. The mature heterocysts contain no functional photosystem II and cannot produce oxygen. Instead, they contain only photosystem I, which enables them to carry out cyclic photophosphorylation and ATP regeneration. These changes provide the appropriate conditions for the functioning of the oxygen-sensitive nitrogenase
Bacterial, archaeal or viral protein belonging to a toxin-antitoxin (TA) system. Toxin protein expression is poisonous to the cell and is counteracted by its co-expressed, short-lived "antidote" antitoxin Antitoxins can be protein (type II, IV, V, VI) or RNA (type I, III) and act directly or indirectly on the toxin protein or transcript Genes for the 2 components are closely linked; in many type II TA systems the toxin-antitoxin complex regulates transcription of its operon. Toxins belong to recognizable protein families, antitoxins usually do not. Orphan toxin genes are occasionally found in complete genomes
Viral protein necessary for the penetration of the viral genome into the host cell nucleus either via active nuclear transport through nuclear pore complexes (NPCs) or DNA injection through the nuclear membrane. Nuclear membrane permeabilization might also be possible Viruses can also enter the nucleus during mitosis when the nuclear membrane temporarily disintegrates (e.g. most retroviruses). All these strategies to cross the nuclear envelope barrier are associated with various levels of capsid disassembly, since virus can pass intact (e.g. papovaviruses) or, in the case of injection, only the viral genome enters the nucleus (e.g. herpesviruses)
Viral protein that allows the active transport of complete particles and viral components along microtubules toward the intracellular replication sites during virus entry. This transport, which usually involves motor proteins like dynein or polymerization/depolymerization reactions as a driving force, is mostly used by viruses that replicate their genome near or in the nucleus. Neurotropic viruses for example, often enter neurons at the terminal axon and their viral genome must be moved retrogradely to cell bodies. Viruses such as adenovirus, Adeno-associated virus, rabies virus, canine parvovirus, vaccinia, foamy virus, human papillomavirus 16 and herpes virus utilize this type of intracellular transport
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