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YojI of Escherichia coli functions as a microcin J25 efflux pump

Mónica A Delgado1, Paula A Vincent, Ricardo N Farías

  • 1Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán), San Miguel de Tucumán, Argentina.

Journal of Bacteriology
|May 4, 2005
PubMed

Insights

Escherichia coli YojI protein exports the peptide antibiotic microcin J25, conferring cellular resistance. This export mechanism, requiring the TolC outer membrane protein, prevents toxic intracellular microcin J25 accumulation.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Physiology

Background:

  • Escherichia coli yojI is an open reading frame with an uncharacterized function.
  • YojI was previously predicted to be an ATP-binding-cassette (ABC) transporter based on sequence homology.
  • The peptide antibiotic microcin J25 (MccJ25) exhibits antimicrobial activity against various bacteria.

Purpose of the Study:

  • To elucidate the function of the Escherichia coli YojI protein.
  • To investigate the role of YojI in resistance to the peptide antibiotic microcin J25.
  • To determine if YojI acts as an exporter for microcin J25.

Main Methods:

  • Gene expression analysis of yojI in Escherichia coli.
  • Microcin J25 sensitivity assays in wild-type and mutant strains.
  • Bacterial two-hybrid assays to assess protein-protein interactions.
  • Demonstration of YojI's ability to efflux microcin molecules.

Main Results:

  • Overexpression of yojI from a multicopy vector conferred resistance to microcin J25.
  • Disruption of the chromosomal yojI gene increased sensitivity to microcin J25.
  • YojI was shown to actively transport microcin J25 out of the cell.
  • The outer membrane protein TolC was found to be essential for microcin J25 export mediated by YojI.

Conclusions:

  • YojI functions as an exporter for microcin J25 in Escherichia coli.
  • The YojI-TolC system prevents the accumulation of toxic intracellular concentrations of microcin J25.
  • Microcin J25 is the first identified substrate for the YojI exporter.

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