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RamB, a novel transcriptional regulator of genes involved in acetate metabolism of Corynebacterium glutamicum.

ABSTRACT: The adaptation of Corynebacterium glutamicum to acetate as a carbon and energy source involves transcriptional regulation of the pta-ack operon coding for the acetate-activating enzymes phosphotransacetylase and acetate kinase and of the aceA and aceB genes coding for the glyoxylate cycle enzymes isocitrate lyase and malate synthase, respectively. Deletion and mutation analysis of the respective promoter regions led to the identification of highly conserved 13-bp motifs (AA/GAACTTTGCAAA) as cis-regulatory elements for expression of the pta-ack operon and the aceA and aceB genes. By use of DNA affinity chromatography, a 53-kDa protein specifically binding to the promoter/operator region of the pta-ack operon was purified. Mass spectrometry and peptide mass fingerprinting identified the protein as a putative transcriptional regulator (which was designated RamB). Purified His-tagged RamB protein was shown to bind specifically to both the pta-ack and the aceA/aceB promoter/operator regions. Directed deletion of the ramB gene in the genome of C. glutamicum resulted in mutant strain RG1. Whereas the wild type of C. glutamicum showed high-level specific activities of acetate kinase, phosphotransacetylase, isocitrate lyase, and malate synthase when grown on acetate and low-level specific activities when grown on glucose as sole carbon and energy sources, mutant RG1 showed high-level specific activities with all four enzymes irrespective of the substrate. Comparative transcriptional cat fusion experiments revealed that this deregulation takes place at the level of transcription. The results indicate that RamB is a negative transcriptional regulator of genes involved in acetate metabolism of C. glutamicum.

SUBMITTER: Gerstmeir R

PROVIDER: S-EPMC387790 | biostudies-literature | 2004 May

REPOSITORIES: biostudies-literature

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RamB, a novel transcriptional regulator of genes involved in acetate metabolism of Corynebacterium glutamicum.

Gerstmeir Robert R Cramer Annette A Dangel Petra P Schaffer Steffen S Eikmanns Bernhard J BJ

Journal of bacteriology 20040501 9

The adaptation of Corynebacterium glutamicum to acetate as a carbon and energy source involves transcriptional regulation of the pta-ack operon coding for the acetate-activating enzymes phosphotransacetylase and acetate kinase and of the aceA and aceB genes coding for the glyoxylate cycle enzymes isocitrate lyase and malate synthase, respectively. Deletion and mutation analysis of the respective promoter regions led to the identification of highly conserved 13-bp motifs (AA/GAACTTTGCAAA) as cis- ...[more]

PMID: 15090522

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Project description:BackgroundThe knowledge about complete bacterial genome sequences opens the way to reconstruct the qualitative topology and global connectivity of transcriptional regulatory networks. Since iron is essential for a variety of cellular processes but also poses problems in biological systems due to its high toxicity, bacteria have evolved complex transcriptional regulatory networks to achieve an effective iron homeostasis. Here, we apply a combination of transcriptomics, bioinformatics, in vitro assays, and comparative genomics to decipher the regulatory network of the iron-dependent transcriptional regulator DtxR of Corynebacterium glutamicum.ResultsA deletion of the dtxR gene of C. glutamicum ATCC 13032 led to the mutant strain C. glutamicum IB2103 that was able to grow in minimal medium only under low-iron conditions. By performing genome-wide DNA microarray hybridizations, differentially expressed genes involved in iron metabolism of C. glutamicum were detected in the dtxR mutant. Bioinformatics analysis of the genome sequence identified a common 19-bp motif within the upstream region of 31 genes, whose differential expression in C. glutamicum IB2103 was verified by real-time reverse transcription PCR. Binding of a His-tagged DtxR protein to oligonucleotides containing the 19-bp motifs was demonstrated in vitro by DNA band shift assays. At least 64 genes encoding a variety of physiological functions in iron transport and utilization, in central carbohydrate metabolism and in transcriptional regulation are controlled directly by the DtxR protein. A comparison with the bioinformatically predicted networks of C. efficiens, C. diphtheriae and C. jeikeium identified evolutionary conserved elements of the DtxR network.ConclusionThis work adds considerably to our currrent understanding of the transcriptional regulatory network of C. glutamicum genes that are controlled by DtxR. The DtxR protein has a major role in controlling the expression of genes involved in iron metabolism and exerts a dual regulatory function as repressor of genes participating in iron uptake and utilization and as activator of genes responsible for iron storage and DNA protection. The data suggest that the DtxR protein acts as global regulator by controlling the expression of other regulatory proteins that might take care of an iron-dependent regulation of a broader transcriptional network of C. glutamicum genes.

Dataset Information

RamB, a novel transcriptional regulator of genes involved in acetate metabolism of Corynebacterium glutamicum.

Publications

RamB, a novel transcriptional regulator of genes involved in acetate metabolism of Corynebacterium glutamicum.

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