COLICINS - EXOCELLULAR LETHAL PROTEINS OF ESCHERICHIA-COLI

Colicins are toxic exoproteins produced by bacteria of colicinogenic s trains of Escherichia coli and some related species of Enterobacteriac eae, during the growth of their cultures. They inhibit sensitive bacte ria of the same family. About 35 % E. coli strains appearing in human intestinal tract are colicinogenic. Synthesis of colicins is coded by genes located on Col plasmids. Until now more than 34 types of colicin s have been described, 21 of them in greater detail, vir. colicins A, B, D, E1-E9, Ia, Ib, J(S), K, M, N, U, 5, 10. In general, their intera ction with sensitive bacteria includes three steps: (I) binding of the colicin molecule to a specific receptor in the bacterial outer membra ne; (2) its translocation through the cell envelope; and (3) its letha l interaction with the specific molecular target in the cell. The clas sification of colicins is based on differences in the molecular events of these three steps.