8.B.24 The Colicin Immunity Protein (ColIP) Functional Family
Proteins conferring immunity against pore-forming colicins are localized in the E. coli inner membrane. Their protective effects are mediated by direct interaction with the C-terminal domain of their cognate colicins. Cai, the immunity protein protecting E. coli against colicin A, contains four cysteine residues. Cai forms homodimers with four TMSs per subunit, and dimerization occurs via the third TMS. Co-expression of Cai with its target, the colicin A pore-forming domain (pfColA), in the inner membrane prevents the formation of intermolecular and intramolecular disulfide bonds, indicating that pfColA interacts with the dimer of Cai and modifies its conformation. When Cai is locked by disulfide bonds, it is no longer able to protect cells against colicin A (Zhang et al. 2010).
This family includes several subfamilies with very different protein sizes, topologies (from 0 to 4 TMSs) and sequences, and their target proteins inhibit colicins that act in very different ways. Homology between members of these different subfamilies has not been established, so the ColIP family should be consider to be a functional superfamily.
References:
Colicin immunity protein of 178 aas and 4 TMSs; 61 % identical to Cai of E. coli which also has 4 TMSs (Zhang et al. 2010).
Proteobacteria
Colicin immunity protein of Citrobacter freundii
Colicin N immunity Protein of 131 aas and 3 or 4 TMSs
Proteobacteria
Imm of E. coli
Putative Colicin Immunity protein of 148 aas and 4 TMSs.
Proteobacteria
Imm of Providencia alcalifaciens
Immunity protein, ImnH, of 184 aas and 4 TMSs; provides immunity to the colicin-like pore-forming domain protein, PmnH (TC#1.C.1.3.6) (Ghequire et al. 2017).
ImnH of Pseudomonas synxantha
Colicin U immunity protein, Cui, of 174 aas and 4 TMSs (Smajs et al. 2006).
Cui of Shigella boydii
Colicin Ib immunity protein of 127 aas and 3 TMSs, Imm.
Proteobacteria
Imm of E. coli
Alveicin A immunity protein of 111 aas and 3 TMSs (Wertz and Riley 2004).
Proteobacteria
Alveicin A immunity protein of Hafnia alvei
Uncharacted protein of 103 aas and 3 TMSs
Proteobacteria
UP of Aeromonas hydrophila
Uncharacterized protein of 131 aas and 3 TMSs
Proteobacteria
UP of Aggregatibacter actinomycetemcomitans
Uncharacterized protein of 117 aas and 4 TMSs
Proteobacteria
UP of Salmonella enterica subsp. enterica serovar Tallahassee
Colicin immunity protein of 119 aas and 3 TMSs, Imm.
Proteobacteria
Imm of E. coli
Colicin M Immunity Protein of 141 aas and 1 TMSs. Cmi. This protein is able to protect a cell that harbors the plasmid ColBM-Cl139 encoding colicin M, against colicin M. Colicin M (Cma) is inactivated by interaction with Cmi. The structure of Cmi has been solved at a resolution of 1.95Å. The monomeric structure consists of a long N-terminal α-TMS and a four-stranded C-terminal β-sheet. Dimerization is mediated by an extended interface of hydrogen bond interactions between the α-helix and the four-stranded β-sheet of the symmetry related molecule. Two intermolecular disulfide bridges covalently connect this dimer to lock this complex (Usón et al. 2012).
Proteobacteria
Cmi of E. coli
YebF homologue of 119 aas and 1 TMS.
Proteobacteria
YebF homologue of Hafnia alvei
Uncharacterized protein of 113 aas and 1 TMS.
Proteobacteria
UP of Salmonella enterica
Colicin E3 immunity protein of 85 aas and 0 TMSs, Imm3, Imm, ImmB, CeiC.
Proteobacteria
ImmB (CeiC) of E. coli
Cloacin of 92 aas and 0 TMSs.
Proteobacteria
Cloacin of Pseudomonas fluorescens
Uncharacterized protein of 79 aas and 0 TMSs
Cyanobacteria
UP of Synechococcus sp.
Colicin E8 immunity protein of 85 aas and 0 TMSs.
Proteobacteria
Imm of E. coli
Pyocin S2 immunity protein of 86 aas
Proteobacteria
Pyocin immunity protein of Pseudomonas plecoglossicida
bacteriocin immunity protein of 83 aas and 0 TMSs
Proteobacteria
Immunity protein of Acaryochloris marina
Uncharacterized protein of 83 aas and 0 TMSs
Actinobacteria
UP of Streptomyces gancidicus
Colicin E7 immunity protein of 87 aas, Imm; Im7; CeiE7 (Knowling et al. 2009).
Proteobacteria
Imm or CeiE7 of E. coli