title: Identification and characterization of a bacterial transport system for the uptake of pyruvate, propionate, and acetate in Corynebacterium glutamicum.
abstract: The metabolism of monocarboxylic acids is of central importance for bacteria in their natural habitat as well as during biotechnological production. Although biosynthesis and degradation are well understood, the transport of such compounds is still a matter of discussion. Here we present the identification and characterization of a new transport system in Corynebacterium glutamicum with high affinity for acetate and propionate and with lower affinity for pyruvate. Biochemical analysis of this monocarboxylic acid transporter (MctC) revealed for the first time a quantitative discrimination of passive diffusion and active transport of acetate by bacterial cells. MctC is a secondary transporter and belongs to the class of sodium solute symporters, but it is driven by the electrochemical proton potential. The mctC gene is preceded by and cotranscribed with cg0952, a locus encoding a small membrane protein, and the transcription of the cg0952-mctC operon is under the control of the transcriptional regulators RamA and RamB. Both of these proteins directly bind to the promoter region of the operon; RamA is essential for expression and RamB exerts a slightly negative control on expression of the cg0952-mctC operon. mctC expression is induced in the presence of pyruvate and beneficial under substrate-limiting conditions for C. glutamicum.
authors.affiliation: Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Jolkver
authors.forename: Denise
authors.initials: D
authors.lastname: Emer
authors.forename: Stefan
authors.initials: S
authors.lastname: Ballan
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
authors.forename: Kay
authors.initials: K
authors.lastname: Marin
mesh_terms: D000085:Acetates / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D027501:Monocarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011422:Propionates / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000085:Acetates; D001426:Bacterial Proteins; D027501:Monocarboxylic Acid Transporters; D011422:Propionates; D019289:Pyruvic Acid