Structural and functional characterization of microcin C resistance peptidase MccF from Bacillus anthracis

International Conference and Exhibition on Metabolomics & Systems Biology

20-22 February 2012 San Francisco Airport Marriott Waterfront, USA

A. Joachimiak, B. Nocek, A. Tikhonov, M. Gu1, K. S. Makarova, G. Vondenhoff, A. Van Aerschot and K. Severinov

Scientific Tracks Abstracts: J Comput Sci Syst Biol

Abstract :

Microcin C (McC) is heptapeptide-adenylate antibiotic produced by Escherichia coli strains carrying the mccABCDEF gene cluster encoding, in addition to the heptapeptide structural gene mccA , enzymes necessary for McC biosynthesis and self- immunity of the producing cell. The heptapeptide facilitates McC transport into susceptible cells, where it is processed releasing a non-hydrolyzable aminoacyl adenylate that inhibits an essential aspartyl-tRNA synthetase. The self-immunity gene mccF encodes a specialized serine-peptidase that cleaves an amide bond connecting the peptidyl or aminoacyl moieties of, respectively, intact and processed McC with the nucleotidyl moiety. Unlike in E. coli , some of mccF orthologs are not expressed as a part of the mcc operon, and exist as single genes. Here, we show that a protein product of one such gene, MccF from Bacillus anthracis ( Ba MccF), is able to cleave intact and processed McC. Structural analysis conformed this observation. The structures of apo- Ba MccF and its AMP-complex revealed a peptidase with specific features that allow MccF to interact with substrates containing nucleotidyl moieties. Sequence analysis and phylogenetic tree reconstruction for the MccF/LD-carboxypeptidase family of proteins show distinct subfamilies in the MccF clade. Several representatives of MccF clade can restore E. coli resistance to McC and other non-hydrolyzable aminoacyl adenylates. Based on our data we propose that members of MccF clade may have similar substrate specificity. Our results suggest that expression of widespread mccF -like genes may be linked to detoxification of aminoacyl adenylates (endogenous or exogenous) and may represent a ?stealthy? source of antibiotic resistance.