The structure of microcin C51, a new antibiotic produced by E. coli, has been determined. This antibiotic was shown to be a 1.18 kDa nucleotide peptide. It consists of a heptapeptide with formylmethionine as the N-terminus and a C-terminal asparagine linked with nebularin-5′-monophosphate through the three-methylene bridge. The OH-group of threonine is substituted. The peptide chain of microcin C51 synthesized on ribosomes is the longest among the known biologically active nucleotide peptides.
