| Description | Competence is the ability of a cell to take up exogenous DNA from its environment, resulting in transformation. It is widespread among bacteria and is probably an important mechanism for the horizontal transfer of genes. DNA usually becomes available by the death and lysis of other cells. Competent bacteria use components of extracellular filaments called type 4 pili to create pores in their membranes and pull DNA through the pores into the cytoplasm. This process, including the development of competence and the expression of the uptake machinery, is regulated in response to cell-cell signalling and/or nutritional conditions [ ].This family consists of streptococcal competence stimulating peptide precursors, which are generally up to 50 amino acid residues long. In all the members of this family, the leader sequence is cleaved after two conserved glycine residues; thus the leader sequence is of the double- glycine type [ ]. Competence stimulating peptides (CSP) are small (less than 25 amino acid residues) cationic peptides. The N-terminal amino acid residue is negatively charged, either glutamate or aspartate. The C-terminal end is positively charged. The third residue is also positively charged: a highly conserved arginine []. Some COMC proteins and their precursors (not included in this family) do not fully follow the above description.Functionally, CSP act as pheromones, stimulating competence for genetic transformation in streptococci. In streptococci, the (CSP mediated) competence response requires exponential cell growth at a critical density, a relatively simple requirement when compared to the stationary-phase requirement of Haemophilus, or the late-logarithmic- phase of Bacillus [ ]. All bacteria induced to competence by a particular CSP are said to belong to the same pherotype, because each CSP is recognised by a specific receptor (the signalling domain of a histidine kinase ComD). Pherotypes are not necessarily species-specific. In addition, an organism may change pherotype. There are two possible mechanisms for pherotype switching: horizontal gene transfer, and accumulation of point mutations. The biological significance of pherotypes and pherotype switching is not definitively determined. Pherotype switching occurs frequently enough in naturally competent streptococci to suggest that it may be an important contributor to genetic exchange between different bacterial species [].This entry also includes proteins that form bacteriocin-like propetides with a glycine-glycine cleavage site. The bacteriocin is initially formed as a pre-propeptide and upon cleavage at the glycine-glycine cleavage site, a leader peptide and the propeptide would be formed. The propeptide then undergoes posttranslational modification before becoming functional [ ]. | Name | Competence protein, ComC |
| Short Name | Competence_ComC | Type | Family |
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