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Wei, Y, Guffanti, AA, Ito, M and Krulwich, TA (2000) Bacillus subtilis YqkI is a novel malic/Na+-lactate antiporter that enhances growth on malate at low protonmotive force. J. Biol. Chem. 275:30287-92


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.


PubMed Online version:10.1074/jbc.M001112200


Antiporters/genetics; Antiporters/metabolism; Bacillus subtilis/genetics; Bacillus subtilis/growth & development; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biological Transport, Active/drug effects; Biological Transport, Active/genetics; Carrier Proteins/genetics; Carrier Proteins/metabolism; Cation Transport Proteins; Cations, Monovalent/metabolism; Escherichia coli/genetics; Genes, Bacterial; Genetic Complementation Test; Ionophores/pharmacology; Lactic Acid/metabolism; Malates/metabolism; Proton-Motive Force; Sodium/metabolism



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0015385: sodium:proton antiporter activity



Figure 5

CACAO 11115


See also


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