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The mechanism of microcin C resistance provided by the MccF peptidase

Anton Tikhonov1, Teymur Kazakov, Ekaterina Semenova

  • 1Institutes of Molecular Genetics and Gene Biology, Russian Academy of Sciences, Moscow, Russia.

The Journal of Biological Chemistry
|September 30, 2010
PubMed

Insights

Microcin C (McC) inhibits bacteria, but MccF provides resistance by cleaving the bond between aspartate and the nucleotide. This enzyme detoxifies McC, protecting cells from its potent growth inhibition.

Area of Science:

  • Microbiology
  • Biochemistry
  • Molecular Biology

Background:

  • Microcin C (McC) is a heptapeptide-nucleotide antibiotic that inhibits enteric bacteria.
  • McC is processed intracellularly to release aspartyl-adenylate, a potent inhibitor of aspartyl-tRNA synthetase.
  • The mccABCDE operon confers McC production and resistance, while the adjacent mccF gene also provides resistance.

Purpose of the Study:

  • To elucidate the mechanism by which the mccF gene product confers resistance to Microcin C.
  • To investigate the enzymatic activity of MccF on Microcin C and related compounds.

Main Methods:

  • Biochemical assays to determine the cleavage activity of MccF.
  • Analysis of MccF's substrate specificity using various aminoacyl adenylates and sulfamoyl adenosines.

Main Results:

  • MccF was shown to detoxify both intact and processed Microcin C.
  • MccF cleaves the amide bond linking the C-terminal aspartate to the nucleotide moiety in McC.
  • MccF also cleaves similar bonds in nonhydrolyzable aminoacyl sulfamoyl adenosines, with specificity for aspartyl and glutamyl moieties.

Conclusions:

  • MccF confers resistance to Microcin C by enzymatically cleaving the critical aspartate-nucleotide bond.
  • MccF exhibits carboxypeptidase-like activity, acting on the amide bond within McC and related structures.
  • The findings reveal a novel detoxification mechanism against a potent bacterial toxin.

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