Microcin C7 (McC) is a member of the class of small molecule antimicrobials produced by Enterobacteriaceae. This ‘Trojan horse’ antibiotic consists of a nonhydrolyzable aspartyl–adenylate that is efficiently imported into bacterial cells owing to a covalently attached peptide carrier. Once inside the cell, the carrier is removed by proteolytic processing to release a potent aspartyl tRNA synthetase inhibitor, thereby halting protein synthesis.
The gene MccF from E.coli belongs to the S66 family of serine peptidases (Tikhonov et al, 2010). MccF detoxifies McC in the cell, providing a mechanisms of resistance to McC as a bacteriocidal agent.
Examination of the genomes of isolates of O. tsutsugamushi showed the presence of a single gene with homology to MccF. This Microcin C7 resistance protein occurs in the genome of the Boryong isolate at positions 271149..272147. Examination of the genomes of 14 isolates of O. tsutsugamushi showed the presence of this gene in all isolates and in the genome of O. chuto. As with other genes in O. tsutsugamushi, there is variation between isolates at both the nucleic acid and amino acid level.