Modulation of Activity of
            <i>Bacillus subtilis</i>
            Regulatory Proteins GltC and TnrA by Glutamate Dehydrogenase

Belitsky, Boris R.; Sonenshein, Abraham L.

doi:10.1128/jb.186.11.3399-3407.2004

Cited by 41 publications

(60 citation statements)

References 34 publications

(62 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The explanation in part seems to be that derepressed expression of rocG leads to degradation of endogenous glutamate. Additionally, higher RocG activity may interfere with glutamate synthesis due to inactivation of GltC (6). Reduced expression of glutamate synthase genes in ccpA mutants was documented previously (8,13,30).…”

Section: Discussionmentioning

confidence: 94%

“…As shown in the accompanying paper (6), high activity of GlutDH could drastically alter the regulation of nitrogen metabolism genes due to production of ammonium and consequent inactivation of a global regulator TnrA (14,15,35). In addition, GlutDH interferes with the activity of GltC, the activator of glutamate synthase (6). Interestingly, expression of gudB is also reduced in the presence of glucose, although the mechanism of this regulation remains unknown (7).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

CcpA-Dependent Regulation of Bacillus subtilis Glutamate Dehydrogenase Gene Expression

2004

Self Cite

View full text Add to dashboard Cite

The Bacillus subtilis rocG gene, encoding catabolic glutamate dehydrogenase, was found to be subject to direct CcpA-dependent glucose repression. The effect of CcpA required the presence of both the HPr and Crh proteins. The primary CcpA binding site was identified by mutational analysis and DNase I footprinting. In the absence of inducers of the Roc pathway, rocG was still expressed at a low level due to readthrough transcription. CcpA-dependent repression of rocG readthrough transcription proved to contribute to the slow growth rate of B. subtilis cells in glucose-glutamate medium. Increased readthrough expression of rocG was shown to be partially responsible for the growth defect of ccpA strains in glucose-ammonium medium.Interconversions of ␣-ketoglutarate and glutamate are major links between carbon and nitrogen metabolism. These reactions are catalyzed by several enzymes: glutamate synthase [␣-ketoglutarate ϩ glutamine ϩ NAD(P)H 3 2ϫ glutamate ϩ NAD ϩ (P)], glutamate dehydrogenase (GlutDH) [␣-ketoglutarate ϩ NH 3 ϩ NAD(P)H^glutamate ϩ NAD ϩ (P)], and glutamate-dependent aminotransferases [glutamate ϩ keto acid (or aldehyde)^␣-ketoglutarate ϩ amino acid].In Bacillus subtilis, two genes code for GlutDH proteins. The rocG gene product is the major catabolic GlutDH, while gudB encodes an intrinsically inactive GlutDH (7). Spontaneous gain-of-function mutations in gudB generate a second catabolic GlutDH, GudB1 (7). No anabolic glutamate dehydrogenase is present in B. subtilis, and all de novo synthesis of glutamate is catalyzed by glutamate synthase (3).The B. subtilis rocG gene is a member of the RocR regulon (5). RocR also controls the rocABC and rocDEF operons, whose products catalyze degradation of arginine to glutamate (9,16,17). All three roc transcription units have SigL-dependent promoters, require RocR and AhrC proteins for expression, and are induced by arginine, ornithine, or proline. The RocG-catalyzed reaction (glutamate ϩ NAD ϩ 3 ␣-ketoglutarate ϩ NH 3 ϩ NADH) can be viewed as the final step in the utilization of arginine, ornithine, and proline, providing rapidly metabolizable carbon-or nitrogen-containing compounds for biosynthesis.Many B. subtilis genes involved in utilization of alternative carbon sources are subject to carbon catabolite repression mediated by the CcpA protein (8,11,25,34). We show here that rocG expression is also subject to CcpA-dependent carbon catabolite repression. In the course of this work, we discovered that rocG is transcribed not only from its own SigL-dependent promoter but also by readthrough from an upstream gene. In fact, the known growth defect of ccpA mutants in glucoseammonium medium (13,30,33) can be partially relieved by blocking readthrough transcription of rocG. MATERIALS AND METHODSBacterial strains and culture media. The B. subtilis strains used in this study are listed in Table 1 or described in the table footnotes. The media and growth conditions for B. subtilis and Escherichia coli strains were described previously (7). TSS minimal medium was suppleme...

show abstract

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

CcpA-Dependent Regulation of Bacillus subtilis Glutamate Dehydrogenase Gene Expression

2004

Self Cite

View full text Add to dashboard Cite

show abstract

“…In contrast, the GltC protein activates the gltA promoter in the presence of sugars and in the absence of arginine. In the presence of arginine or in the absence of glucose, RocG is synthesized and binds GltC, thus inactivating it (7,11). In addition, GltC activity is modulated by the direct binding of low-molecular-weight effectors; ␣-ketoglutarate stimulates its activity, whereas glutamate inhibits it (26).…”

mentioning

confidence: 99%

Glutamate Metabolism inBacillus subtilis: Gene Expression and Enzyme Activities Evolved To Avoid Futile Cycles and To Allow Rapid Responses to Perturbations of the System

et al. 2008

View full text Add to dashboard Cite

Glutamate is a central metabolite in all organisms since it provides the link between carbon and nitrogen metabolism. In Bacillus subtilis, glutamate is synthesized exclusively by the glutamate synthase, and it can be degraded by the glutamate dehydrogenase. In B. subtilis, the major glutamate dehydrogenase RocG is expressed only in the presence of arginine, and the bacteria are unable to utilize glutamate as the only carbon source. In addition to rocG, a second cryptic gene (gudB) encodes an inactive glutamate dehydrogenase. Mutations in rocG result in the rapid accumulation of gudB1 suppressor mutations that code for an active enzyme. In this work, we analyzed the physiological significance of this constellation of genes and enzymes involved in glutamate metabolism. We found that the weak expression of rocG in the absence of the inducer arginine is limiting for glutamate utilization. Moreover, we addressed the potential ability of the active glutamate dehydrogenases of B. subtilis to synthesize glutamate. Both RocG and GudB1 were unable to catalyze the anabolic reaction, most probably because of their very high K m values for ammonium. In contrast, the Escherichia coli glutamate dehydrogenase is able to produce glutamate even in the background of a B. subtilis cell. B. subtilis responds to any mutation that interferes with glutamate metabolism with the rapid accumulation of extragenic or intragenic suppressor mutations, bringing the glutamate supply into balance. Similarly, with the presence of a cryptic gene, the system can flexibly respond to changes in the external glutamate supply by the selection of mutations.Among the metabolites of a bacterial cell, glutamate is of central importance. It is this amino acid that stands at the intersection between catabolism and anabolism, i.e., between carbon and nitrogen metabolism. Glutamate is synthesized from ␣-ketoglutarate, an intermediate of the tricarboxylic acid (TCA) cycle, and serves as the amino group donor for nearly all nitrogen-containing metabolites of the cell, besides being one of the proteinogenic amino acids. In agreement with this important aspect of glutamate is the fact that it is one of most abundant metabolites in bacterial cells and that its concentration is high under all conditions of nutrient supply (10,18,36). Moreover, its metabolism must be tightly controlled to guarantee a constant, sufficient supply of this essential intermediate for all anabolic reactions.In the gram-positive soil bacterium Bacillus subtilis, glutamate is synthesized exclusively by the reductive amination of ␣-ketoglutarate by the enzyme glutamate synthase (also called glutamate-oxoglutarate amidotransferase [GOGAT]; encoded by the gltAB operon) (Fig. 1) (3). This enzyme produces two molecules of glutamate from ␣-ketoglutarate and glutamine, the primary product of ammonium assimilation. Of these two molecules, one remains in the cycle, whereas the second can be used for protein biosynthesis or transamination reactions to provide the cell with nitrogen-containing compoun...

show abstract

“…13) Recent study of rocG gene regulation associating catabolite repression and derepression on the expression of GluDH has been reported and it shows the role of GluDH in the deamination reaction. 14) The balance between the rates of glutamate synthesis and degradation is maintained by a series of regulations of the Roc pathway, 15) and RocG activity can be viewed as the final step in the use of arginine, ornithine, or purine as a carbon and nitrogen source. 16) We have cloned rocG from B. subtilis, expressed it in E. coli, and characterized the molecular properties of Bs-GluDH.…”

mentioning

confidence: 99%

Molecular Properties and Enhancement of Thermostability by Random Mutagenesis of Glutamate Dehydrogenase fromBacillus subtilis

Khan

Ito

Kim

et al. 2005

Bioscience, Biotechnology, and Biochemistry

View full text Add to dashboard Cite

Modulation of Activity of Bacillus subtilis Regulatory Proteins GltC and TnrA by Glutamate Dehydrogenase

Cited by 41 publications

References 34 publications

CcpA-Dependent Regulation of Bacillus subtilis Glutamate Dehydrogenase Gene Expression

CcpA-Dependent Regulation of Bacillus subtilis Glutamate Dehydrogenase Gene Expression

Glutamate Metabolism inBacillus subtilis: Gene Expression and Enzyme Activities Evolved To Avoid Futile Cycles and To Allow Rapid Responses to Perturbations of the System

Molecular Properties and Enhancement of Thermostability by Random Mutagenesis of Glutamate Dehydrogenase fromBacillus subtilis

Contact Info

Product

Resources

About