| Description | This is a hydrophobic pore-forming domain found towards the N-terminal of RTX toxins [ ].Secretion of virulence factors in Gram-negative bacteria involves transportation of the protein across two membranes to reach the cell exterior [ , ]. Four principal exotoxin secretion systems have been described. In the type II and IV secretion systems, toxins are first exported to the periplasm by way of a cleaved N-terminal signal sequence; a second set of proteins is used for extracellular transport (type II), or the C terminus of the exotoxin itself is used (type IV). Type III secretion involves at least 20 molecules that assemble into a needle; effector proteins are then translocated through this without need of a signal sequence. In the Type I system, a complete channel is formed through both membranes, and the secretion signal is carried on the C terminus of the exotoxin.The RTX (repeats in toxin) family of cytolytic toxins belong to the Type I secretion system, and are important virulence factors in Gram-negative bacteria, such as Escherichia coli ( ), Actinobacillus pleuropneumoniae ( ) and Kingella kingae ( ). They consist of a hydrophobic pore-forming domain at the N-terminal that harbors four putative transmembrane α-helices, a typical glycine-rich repeats segment and a C-terminal signal sequence [ ]. The glycine-rich repeats are essential for binding calcium, and are critical for the biological activity of the secreted toxins []. They can be divided into two different groups, (i) hemolysins, which cause cause the lysis of erythrocytes and exhibit toxicity towards a wide range of cell types from various species; and (ii) leukotoxins, that exhibit narrow cell type and species specificity due to cell-specific binding through the beta2-integrins expressed on the cell surface of leukocytes []. All RTX toxin operons exist in the order rtxCABD, RtxA protein being the structural component of the exotoxin, both RtxB and D being required for its export from the bacterial cell; RtxC is an acyl-carrier-protein-dependent acyl-modification enzyme, required to convert RtxA to its active form [].Escherichia coli haemolysin (HlyA) is often quoted as the model for RTX toxins. Recent work on its relative rtxC gene product HlyC [ ] has revealed that it provides the acylation aspect for post-translational modification of two internal lysine residues in the HlyA protein. To cause pathogenicity, the HlyA toxin must first bind Ca2+ ions to the set of glycine-rich repeats and then be activated by HlyC []. This has been demonstrated both in vitroand in vivo. | Name | RTX, pore-forming domain |
| Short Name | RTX_pore_form | Type | Domain |
Powered by
Have you tried our InterMine mobile apps?
and interoperation is funded by 
