title: Bacillus subtilis YqkI is a novel malic/Na+-lactate antiporter that enhances growth on malate at low protonmotive force.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wei
authors.forename: A A
authors.initials: AA
authors.lastname: Guffanti
authors.forename: M
authors.initials: M
authors.lastname: Ito
authors.forename: T A
authors.initials: TA
authors.lastname: Krulwich
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins; D002414:Cations, Monovalent / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D007476:Ionophores / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism*; D008293:Malates / Q000378:metabolism*; D018892:Proton-Motive Force; D012964:Sodium / Q000378:metabolism*
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002414:Cations, Monovalent; D007476:Ionophores; C414624:MLEN protein, Bacillus subtilis; D008293:Malates; D019344:Lactic Acid; C030298:malic acid; D012964:Sodium