The gene yghK linked to the glc operon of Escherichia coli encodes a permease for glycolate that is structurally and functionally similar to L-lactate permease.
In Escherichia coli the glc operon involved in glycolate utilization is located at 67.3 min and formed by genes encoding the enzymes glycolate oxidase (glcDEF) and malate synthase G (glcB). Their expression from a single promoter upstream of glcD is induced by growth on glycolate and regulated by the activator encoded by the divergently transcribed gene glcC. Gene yghK, located 350 bp downstream of glcB, encodes a hydrophobic protein highly similar to the L-lactate permease encoded by lldP. Expression studies have shown that the yghK gene (proposed name glcA) is transcribed from the same promoter as the other glc structural genes and thus belongs to the glc operon. Characterization of a glcA::cat mutant showed that GlcA acts as glycolate permease and that glycolate can also enter the cell through another transport system. Evidence is presented of the involvement of L-lactate permease in glycolate uptake. Growth on this compound was abolished in a double mutant of the paralogous genes glcA and lldP, and restored with plasmids expressing either GlcA or LldP. Characterization of the putative substrates for these two related permeases showed, in both cases, specificity for the 2-hydroxymonocarboxylates glycolate, L-lactate and D-lactate. Although both GlcA and LldP recognize D-lactate, mutant analysis proved that L-lactate permease is mainly responsible for its uptake.
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain1.
M Felisa
MF
Núñez
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain1.
M
M
Teresa Pellicer
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain1.
Josefa
J
Badı A
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain1.
Juan
J
Aguilar
Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain1.
Laura
L
Baldomà
D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005798:Genes, Bacterial; D006016:Glycolates / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D008292:Malate Synthase / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009876:Operon; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
D006016:Glycolates; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C031149:glycolic acid; D019344:Lactic Acid; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase; D008292:Malate Synthase