title: Citrate synthase in Corynebacterium glutamicum is encoded by two gltA transcripts which are controlled by RamA, RamB, and GlxR.
abstract: Citrate synthase (CS) is located at a major branch point in the metabolism and is required for both tricarboxylic acid and glyoxylic acid cycle activity. Here we show that the CS gene gltA of Corynebacterium glutamicum is monocistronic, but that two transcripts are formed with their transcript initiation sites located 121 bp and 357 bp upstream of the translational start codon, respectively. Northern blot analyses revealed that during growth on acetate the short transcript prevails, whereas during growth on glucose the long transcript is dominant. Further Northern blots, reporter gene fusions, and CS activity measurements in mutants devoid of the transcriptional regulators RamA and RamB or with the global regulator GlxR overexpressed revealed a complex involvement of these regulators in gltA transcription. This was confirmed by demonstrating the direct interaction of isolated RamA, RamB and GlxR proteins with specific gltA promoter regions in vitro. The combined analyses point to an elaborate control of gltA transcript formation, which is possibly required as a dedicated mechanism to balance the total CS activity according to the physiological requirements.
authors.affiliation: Institute of Biotechnology, Forschungszentrum Jülich GmbH, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: van Ooyen
authors.forename: Denise
authors.initials: D
authors.lastname: Emer
authors.forename: Michael
authors.initials: M
authors.lastname: Bussmann
authors.forename: Michael
authors.initials: M
authors.lastname: Bott
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
authors.forename: Lothar
authors.initials: L
authors.lastname: Eggeling
mesh_terms: D000085:Acetates / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000235:genetics* / Q000378:metabolism; D018387:Codon, Initiator; D048230:Corynebacterium glutamicum / Q000201:enzymology* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000085:Acetates; D001426:Bacterial Proteins; D018387:Codon, Initiator; D014157:Transcription Factors; D002950:Citrate (si)-Synthase; D005947:Glucose