Microcin E492, a low-molecular-weight peptide antibiotic which causes depolarization of the Escherichia coli cytoplasmic membrane.

Microcin E492 is a 5,000- to 7,000-molecular-weight peptide antibiotic which depolarizes the cytoplasmic membrane of sensitive Escherichia coli K-12 cells. The microcin has many features in common with colicin V but is distinguished from it by the absence of microcin E472 immunity in ColV+ strains and by the fact that colicin V-insensitive Cir mutants of E. coli K-12 are microcin sensitive. Neither of the two plasmids detected in the producing strain of Klebsiella pneumoniae appear to carry the determinants for microcin E492 production or immunity, which is in contrast to the situation found hitherto with other microcins and colicins.