Immunity proteins: enzyme inhibitors that avoid the active site.
Immunity proteins are high affinity inhibitors of colicins--SOS-induced toxins released by bacteria during times of stress. Recent work has shown that nuclease-specific immunity proteins are exosite inhibitors, binding adjacent to the enzyme active site and inhibiting colicin activity indirectly. Unusually, their binding sites comprise a near contiguous sequence that lies N-terminal to active site sequences, raising the possibility that immunity proteins bind colicins co-translationally. Exosite binding accounts for the extensive sequence diversity seen at the interfaces of colicin-immunity protein complexes, which is not only a selective advantage to colicin-producing bacteria, but also represents a powerful model system for studying specificity in protein-protein recognition.
Kleanthous
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School of Biological Sciences, University of East Anglia, Norwich, UK NR4 7TJ. c.kleanthous@uea.ac.uk
Walker
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D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology*; D001665:Binding Sites; D005075:Biological Evolution; D003087:Colicins / Q000037:antagonists & inhibitors / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000276:immunology*; D007700:Kinetics; D046911:Macromolecular Substances; D008954:Models, Biological; D008958:Models, Molecular
D001426:Bacterial Proteins; D003087:Colicins; D004791:Enzyme Inhibitors; D046911:Macromolecular Substances