The gene yjcG, cotranscribed with the gene acs, encodes an acetate permease in Escherichia coli.
We isolated an Escherichia coli mutant strain that suppresses the glycolate-negative phenotype of a strain deficient in both GlcA and LldP transporters of this compound. This suppressing phenotype was assigned to yjcG, a gene whose function was previously unknown, which was found to encode a membrane protein able to transport glycolate. On the basis of sequence similarity, the yjcG gene product was classified as a member of the sodium:solute symporter family. Northern experiments revealed that yjcG is cotranscribed with its neighbor, acs, encoding acetyl coenzyme A synthetase, which is involved in the scavenging acetate. The fortuitous presence of an IS2 element in acs, which impaired yjcG expression by polarity in our parental strain, allowed us to conclude that the alternative glycolate carrier became active after precise excision of IS2 in the suppressed strain. The finding that yjcG encodes a putative membrane carrier for glycolate and the cotranscription of yjcG with acs suggested that the primary function of the yjcG gene product (proposed gene name, actP) could be acetate transport and allowed us to define an operon involved in acetate metabolism. The time course of [1,2-(14)C]acetate uptake and the results of a concentration kinetics analysis performed with cells expressing ActP or cells deficient in ActP supported the the hypothesis that this carrier is an acetate transporter and suggested that there may be another transport system for this monocarboxylate.
Gimenez
Rosa
R
Department of Biochemistry, School of Pharmacy, University of Barcelona, E-08028 Barcelona, Spain.
Nuñez
María Felisa
MF
Badia
Josefa
J
Aguilar
Juan
J
Baldoma
Laura
L
D000106:Acetate-CoA Ligase / Q000235:genetics* / Q000378:metabolism; D000085:Acetates / Q000378:metabolism*; D001483:Base Sequence; D003470:Culture Media; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics*; D005798:Genes, Bacterial; D006016:Glycolates / Q000378:metabolism; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters / Q000235:genetics* / Q000378:metabolism; D009876:Operon; D013379:Substrate Specificity
D000085:Acetates; C478943:ActP protein, E coli; D003470:Culture Media; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D006016:Glycolates; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; C031149:glycolic acid; D000106:Acetate-CoA Ligase