Transport of L-Lactate, D-Lactate, and glycolate by the LldP and GlcA membrane carriers of Escherichia coli - PubMed (original) (raw)

. 2002 Jan 18;290(2):824-9.

doi: 10.1006/bbrc.2001.6255.

Affiliations

Transport of L-Lactate, D-Lactate, and glycolate by the LldP and GlcA membrane carriers of Escherichia coli

María Felisa Núñez et al. Biochem Biophys Res Commun. 2002.

Abstract

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.

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