The Vibrio cholerae Mrp system: Cation/proton antiport properties and enhancement of bile salt resistance in a heterologous host

Judith Dzioba-Winogrodzki, Olga Winogrodzki, Terry A. Krulwich, Markus A. Boin, Claudia C. Häse, Pavel Dibrov

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

The mrp operon from Vibrio cholerae encoding a putative multisubunit Na+/H+ antiporter was cloned and functionally expressed in the antiporter-deficient strain of Escherichia coli EP432. Cells of EP432 expressing Vc-Mrp exhibited resistance to Na+ and Li+ as well as to natural bile salts such as sodium cholate and taurocholate. When assayed in everted membrane vesicles of the E. coli EP432 host, Vc-Mrp had sufficiently high antiport activity to facilitate the first extensive analysis of Mrp system from a Gram-negative bacterium encoded by a group 2 mrp operon. Vc-Mrp was found to exchange protons for Li+, Na+, and K+ ions in pH-dependent manner with maximal activity at pH 9.0-9.5. Exchange was electrogenic (more than one H+ translocated per cation moved in opposite direction). The apparent Km at pH 9.0 was 1.08, 1.30, and 68.5 mM for Li+, Na+, and K+, respectively. Kinetic analyses suggested that Vc-Mrp operates in a binding exchange mode with all cations and protons competing for binding to the antiporter. The robust ion antiport activity of Vc-Mrp in sub-bacterial vesicles and its effect on bile resistance of the heterologous host make Vc-Mrp an attractive experimental model for the further studies of biochemistry and physiology of Mrp systems.

Original languageEnglish
Pages (from-to)176-186
Number of pages11
JournalJournal of Molecular Microbiology and Biotechnology
Volume16
Issue number3-4
DOIs
StatePublished - Feb 2009

Keywords

  • Bile resistance
  • Heterologous expression
  • Mrp
  • Na(Li)(K)/H antiporter
  • Vibrio cholerae

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