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A high-resolution structure of the DNA-binding domain of AhrC, the arginine repressor/activator protein from Bacillus subtilis.

ABSTRACT: In Bacillus subtilis the concentration of L-arginine is controlled by the transcriptional regulator AhrC, which interacts with 18 bp DNA operator sites called ARG boxes in the promoters of arginine biosynthetic and catabolic operons. AhrC is a 100 kDa homohexamer, with each subunit having two domains. The C-terminal domains form the core, mediating intersubunit interactions and binding of the co-repressor L-arginine, whilst the N-terminal domains contain a winged helix-turn-helix DNA-binding motif and are arranged around the periphery. The N-terminal domain of AhrC has been expressed, purified and characterized and it has been shown that the fragment still binds DNA operators as a recombinant monomer. The DNA-binding domain has also been crystallized and the crystal structure refined to 1.0 A resolution is presented.

SUBMITTER: Garnett JA

PROVIDER: S-EPMC2339755 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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A high-resolution structure of the DNA-binding domain of AhrC, the arginine repressor/activator protein from Bacillus subtilis.

Garnett James A JA Baumberg Simon S Stockley Peter G PG Phillips Simon E V SE

Acta crystallographica. Section F, Structural biology and crystallization communications 20071020 Pt 11

In Bacillus subtilis the concentration of L-arginine is controlled by the transcriptional regulator AhrC, which interacts with 18 bp DNA operator sites called ARG boxes in the promoters of arginine biosynthetic and catabolic operons. AhrC is a 100 kDa homohexamer, with each subunit having two domains. The C-terminal domains form the core, mediating intersubunit interactions and binding of the co-repressor L-arginine, whilst the N-terminal domains contain a winged helix-turn-helix DNA-binding mot ...[more]

PMID: 18007039

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Project description:Streptococcus mutans is a primary cariogenic pathogen in humans. Arginine metabolism is required for bacterial growth. In S. mutans, however, the involvement of transcription factors in regulating arginine metabolism is unclear. The purpose of this study was to investigate the function and mechanism of ArgR family transcription factors in S. mutans. Here, we identified an ArgR (arginine repressor) family transcription factor named AhrC, which negatively regulates arginine biosynthesis and biofilm formation in S. mutans. The ahrC in-frame deletion strain exhibited slow growth and significantly increased intracellular arginine content. The strain overexpressing ahrC showed reduced intracellular arginine content, decreased biofilm biomass, reduced production of water-insoluble exopolysaccharides (EPS), and different biofilm structures. Furthermore, global gene expression profiles revealed differential expression levels of 233 genes in the ahrC-deficient strain, among which genes related to arginine biosynthesis (argJ, argB, argC, argD, argF, argG, argH) were significantly upregulated. In the ahrC overexpression strain, there are 89 differentially expressed genes, mostly related to arginine biosynthesis. The conserved DNA patterns bound by AhrC were identified by electrophoretic mobility shift assay (EMSA) and DNase I footprinting. In addition, the analysis of β-galactosidase activity showed that AhrC acted as a negative regulator. Taken together, our findings suggest that AhrC is an important transcription factor that regulates arginine biosynthesis gene expression and biofilm formation in S. mutans. These findings add new aspects to the complexity of regulating the expression of genes involved in arginine biosynthesis and biofilm formation in S. mutans. IMPORTANCE Arginine metabolism is essential for bacterial growth. The regulation of intracellular arginine metabolism in Streptococcus mutans, one of the major pathogens of dental caries, is unclear. In this study, we found that the transcription factor AhrC can directly and negatively regulate the expression of N-acetyl-gamma-glutamyl-phosphate reductase (argC), thus regulating arginine biosynthesis in S. mutans. In addition, the ahrC overexpression strain exhibited a significant decrease in biofilm and water-insoluble extracellular polysaccharides (EPS). This study adds new support to our understanding of the regulation of intracellular arginine metabolism in S. mutans.

Dataset Information

A high-resolution structure of the DNA-binding domain of AhrC, the arginine repressor/activator protein from Bacillus subtilis.

Publications

A high-resolution structure of the DNA-binding domain of AhrC, the arginine repressor/activator protein from Bacillus subtilis.

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