Author:

Keywords:

transfer-rna synthetase, genetic-determinants, escherichia-coli, agrocin 84, specificity, immunity, cloning, c51, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, TRANSFER-RNA SYNTHETASE, GENETIC-DETERMINANTS, ESCHERICHIA-COLI, AGROCIN 84, SPECIFICITY, IMMUNITY, CLONING, C51, Aspartate-tRNA Ligase, Bacteriocins, Drug Resistance, Bacterial, Enzyme Inhibitors, Escherichia coli, Escherichia coli Proteins, Operon, Peptide Hydrolases, Peptidoglycan, 03 Chemical Sciences, 06 Biological Sciences, 11 Medical and Health Sciences, 31 Biological sciences, 32 Biomedical and clinical sciences, 34 Chemical sciences

Abstract:

The heptapeptide-nucleotide microcin C (McC) is a potent inhibitor of enteric bacteria growth. Inside a sensitive cell, McC is processed by aminopeptidases, which release a nonhydrolyzable aspartyl-adenylate, a strong inhibitor of aspartyl-tRNA synthetase. The mccABCDE operon is sufficient for McC production and resistance of the producing cell to McC. An additional gene, mccF, which is adjacent to but not part of the mccABCDE operon, also provides resistance to exogenous McC. MccF is similar to Escherichia coli LdcA, an L,D-carboxypeptidase whose substrate is monomeric murotetrapeptide L-Ala-D-Glu-meso-A(2)pm-D-Ala or its UDP-activated murein precursor. The mechanism by which MccF provides McC resistance remained unknown. Here, we show that MccF detoxifies both intact and processed McC by cleaving an amide bond between the C-terminal aspartate and the nucleotide moiety. MccF also cleaves the same bond in nonhydrolyzable aminoacyl sulfamoyl adenosines containing aspartyl, glutamyl, and, to a lesser extent, seryl aminoacyl moieties but is ineffective against other amino-acyl adenylates.