Bacillus subtilis YqkI is a novel malic/Na+-lactate antiporter that enhances growth on malate at low protonmotive force

Yi Wei, Arthur A. Guffanti, Masahiro Ito, Terry A. Krulwich

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62 Scopus citations

Abstract

Bacillus subtilis yheL encodes a Na+/H+ antiporter, whereas its paralogue, yqkI, encodes a novel antiporter that achieves a simultaneous Na+/H+ and malolactate antiport. B. subtilis yufR, a control in some experiments, encodes a Na+/malate symporter. YqkI complemented a malate transport mutant of Escherichia coli if Na+ and lactate were present. YheL conferred Na+ uptake capacity on everted membrane vesicles from an antiporter-deficient E. coli mutant that was consistent with a secondary Na+/H+ antiport, but YqkI-dependent Na+ uptake depended on intravesicular malate and extravesicular lactate. YqkI-dependent lactate uptake depended on intravesicular malate and extravesicular Na+. YqkI mediated an electroneutral exchange, which is proposed to be a malic-2-2H+ (or fully protonated malate)/Na+-lactate-1 antiport. Because the composite YqkI-mediated exchanges could be driven by gradients of the malate-lactate pair, this transporter could play a role in growth of B. subtilis on malate at low protonmotive force. A mutant with a disruption of yqkI exhibited an abrupt arrest in the mid-logarithmic phase of growth on malate when low concentrations of protonophore were present. Thus growth of B. subtilis to high density on a putatively nonfermentative dicarboxylic acid substrate depends on a malolactate exchange at suboptimal protonmotive force.

Original languageEnglish
Pages (from-to)30287-30292
Number of pages6
JournalJournal of Biological Chemistry
Volume275
Issue number39
DOIs
StatePublished - 29 Sep 2000

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