1.C.31 The Channel-forming Colicin V (Colicin V) Family
Colicin (Microcin) V is unrelated to other channel-forming colicins (e.g., the Colicin family; TC #1.C.1). The protein is much smaller (103 amino acyl residues) than the other colicins, and it therefore does not form the complex structure characteristic of the homologous members of the colicin family. Colicin V is, however, a pore-forming bacteriocin which exerts its action by inserting into the cytoplasmic membranes of target bacteria and dissipating the membrane potential while facilitating leakage of small molecules from the cytoplasm. In these functional respects (but not structural respects) it therefore resembles channel-forming bacteriocins that are included in the channel-forming amphipathic peptide (CAP) functional superfamily which includes defensins and bacteriocins (e.g., TC families 1.C.16-1.C.30). Colicin V is demonstrably homologous to other proteins such as Microcin L (AAP08989; 105 aas) and the McmA protein (CAD56188; 92 aas), both of E. coli. Colicin V has been shown to depend on the inner membrane SdaC protein (2.A.42.2.1) for its bacteriocidal activity (Gérard et al., 2005). SdaC presumably serves as an inner membrane receptor for Colicin V.
The generalized transport reaction catalyzed by Colicin V is:
ions and small molecules (in) ions and small molecules (out).