Transport of L-Lactate, D-Lactate, and glycolate by the LldP and GlcA membrane carriers of Escherichia coli.
To examine the substrate specificity of the membrane transport carriers LldP (L-lactate permease) and GlcA (glycolate permease) of Escherichia coli, a mutant strain lacking their structural genes and blocked in the metabolism of the tested substrates was constructed and transformed with a plasmid bearing either the lldP or the glcA gene. Each transformant acquired the ability to accumulate L-lactate, D-lactate, and glycolate against a high concentration gradient. Substrate accumulation was inhibited by carbonyl cyanide m-chlorophenylhydrazone, a hydrophobic proton conductor that dissipates proton motive force. Competition of (14)C-L-lactate transport by nonradioactive L-lactate, D-lactate, and glycolate in LldP synthesizing cells and competition of (14)C-glycolate transport by the same three substrates in GlcA synthesizing cells showed that both carriers effectively transported all three substrates with a K(i) value ranging from 10 to 20 microM. D-Lactate does not appear to have a permease of its own. Utilization of the compound depends mainly on LldP.
Núñez
María Felisa
MF
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Avenida Diagonal 643, Barcelona, 08028, Spain.
Kwon
Ohsuk
O
Wilson
T Hastings
TH
Aguilar
Juan
J
Baldoma
Laura
L
Lin
Edmund C C
EC
D019342:Acetic Acid / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D006016:Glycolates / Q000378:metabolism* / Q000493:pharmacokinetics; D019344:Lactic Acid / Q000378:metabolism* / Q000493:pharmacokinetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D011522:Protons; D013237:Stereoisomerism; D013379:Substrate Specificity; D014169:Transformation, Bacterial / Q000235:genetics
D029968:Escherichia coli Proteins; D006016:Glycolates; C083722:LldP protein, E coli; D026901:Membrane Transport Proteins; D011522:Protons; C031149:glycolic acid; D019344:Lactic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D019342:Acetic Acid