Cloacin immunity protein

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PDB 2b5u EBI.jpg
crystal structure of colicin e3 v206c mutant in complex with its immunity protein
Symbol Cloacin_immun
Pfam PF03513
InterPro IPR003063
SCOP 3eip

In molecular biology, the cloacin immunity protein inhibits the bacterial polypeptide toxin, cloacin. It complexes with cloacin in equimolar quantities and inhibits it by binding with high affinity to the cloacin C-terminal catalytic domain. The immunity protein is relatively small, containing 85 amino acids. An extra ribosome binding site has been found to precede the immunity gene on the polycistronic Clo DF13 mRNA,[1] which perhaps accounts for the fact that, in cloacinogenic cells, more immunity protein than cloacin is synthesised.[1] Comparison of the complete amino acid sequence of the Clo DF13 immunity protein with that of the Col E3 and Col E6 immunity proteins reveals extensive similarities in primary structure, although Col E3 and Clo DF13 immunity proteins are exchangeable only to a low extent in vivo and in vitro.[1]


  1. ^ a b c van den Elzen PJ, Gaastra W, Spelt CE, de Graaf FK, Veltkamp E, Nijkamp HJ (October 1980). "Molecular structure of the immunity gene and immunity protein of the bacteriocinogenic plasmid Clo DF13". Nucleic Acids Res. 8 (19): 4349–63. doi:10.1093/nar/8.19.4349. PMC 324244Freely accessible. PMID 6253914. 

This article incorporates text from the public domain Pfam and InterPro IPR003063