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FEBS Lett. 2001 May 11;496(2-3):117-20.

Mrp-dependent Na(+)/H(+) antiporters of Bacillus exhibit characteristics that are unanticipated for completely secondary active transporters.

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  • 1Faculty of Life Scienes, Toyo University, Gunma, Japan. ito1107@toyonet.toyo.ac.jp

Abstract

The Na(+)/H(+) antiport activity encoded by the seven-gene mrp operons of Bacillus subtilis and alkaliphilic Bacillus pseudofirmus OF4 were cloned into a low copy plasmid, were expressed in several Escherichia coli mutant strains and compared side-by-side with similarly cloned nhaA, a major secondary antiporter from E. coli. All three antiporter systems exhibited electron donor-dependent antiport in a fluorescence-based vesicle assay, with NhaA being the most active. In whole cells of the same antiporter-deficient strain from which the vesicles were made, E. coli KNabc, Mrp-mediated Na(+) exclusion was significantly more protonophore-resistant than that conferred by NhaA. The Mrp systems were also more efficacious than NhaA: in supporting anaerobic Na(+) resistance in wild type and a terminal oxidase mutant strain of E. coli (SBS2115); and in increasing non-fermentative growth of an NADH dehydrogenase-minus E. coli mutant (ANN0222). The results suggest the possibility that the Mrp systems may have both secondary and primary energization capacities.

PMID:
11356194
[PubMed - indexed for MEDLINE]
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