inhibitory immunity (Im) protein of colicin (Col) deoxyribonuclease (DNase) and pyocins
This family contains inhibitory immunity (Im) proteins that bind to colicin endonucleases (DNases) or pyocins with very high affinity and specificity; this is critical for the neutralization of endogenous DNase catalytic activity and for protection against exogenous DNase bacteriocins. The DNase colicin family (ColE2, ColE7, ColE8 and ColE9) in E. coli, and pyocin family (S1, S2, S3 and AP41) in P. aeruginosa, are potent bacteriocins where the immunity proteins (Ims) protect the colicin/pyocin producing (i.e. colicinogenic) bacteria by binding and inactivating colicin nucleases. The binding affinities between cognate and non-cognate nucleases by Im proteins can vary up to 10 orders of magnitude.