Dataset Information

Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans.

ABSTRACT: In the dental caries pathogen Streptococcus mutans, phosphotransacetylase (Pta) catalyzes the conversion of acetyl coenzyme A (acetyl-CoA) to acetyl phosphate (AcP), which can be converted to acetate by acetate kinase (Ack), with the concomitant generation of ATP. A ?ackA mutant displayed enhanced accumulation of AcP under aerobic conditions, whereas little or no AcP was observed in the ?pta or ?pta ?ackA mutant. The ?pta and ?pta ?ackA mutants also had diminished ATP pools compared to the size of the ATP pool for the parental or ?ackA strain. Surprisingly, when exposed to oxidative stress, the ?pta ?ackA strain appeared to regain the capacity to produce AcP, with a concurrent increase in the size of the ATP pool compared to that for the parental strain. The ?ackA and ?pta ?ackA mutants exhibited enhanced (p)ppGpp accumulation, whereas the strain lacking Pta produced less (p)ppGpp than the wild-type strain. The ?ackA and ?pta ?ackA mutants displayed global changes in gene expression, as assessed by microarrays. All strains lacking Pta, which had defects in AcP production under aerobic conditions, were impaired in their abilities to form biofilms when glucose was the growth carbohydrate. Collectively, these data demonstrate the complex regulation of the Pta-Ack pathway and critical roles for these enzymes in processes that appear to be essential for the persistence and pathogenesis of S. mutans.

SUBMITTER: Kim JN

PROVIDER: S-EPMC4495203 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans.

Kim Jeong Nam JN Ahn Sang-Joon SJ Burne Robert A RA

Applied and environmental microbiology 20150515 15

In the dental caries pathogen Streptococcus mutans, phosphotransacetylase (Pta) catalyzes the conversion of acetyl coenzyme A (acetyl-CoA) to acetyl phosphate (AcP), which can be converted to acetate by acetate kinase (Ack), with the concomitant generation of ATP. A ΔackA mutant displayed enhanced accumulation of AcP under aerobic conditions, whereas little or no AcP was observed in the Δpta or Δpta ΔackA mutant. The Δpta and Δpta ΔackA mutants also had diminished ATP pools compared to the size ...[more]

PMID: 25979891

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Project description:In the dental caries pathogen Streptococcus mutans, phosphotransacetylase (Pta) and acetate kinase (Ack) convert pyruvate into acetate with the concomitant generation of ATP. The genes for this pathway are tightly regulated by multiple environmental and intracellular inputs, but the basis for differential expression of the genes for Pta and Ack in S. mutans had not been investigated. Here, we show that inactivation in S. mutans of ccpA or codY reduced the activity of the ackA promoter, whereas a ccpA mutant displayed elevated pta promoter activity. The interactions of CcpA with the promoter regions of both genes were observed using electrophoretic mobility shift and DNase protection assays. CodY bound to the ackA promoter region but only in the presence of branched-chain amino acids (BCAAs). DNase footprinting revealed that the upstream region of both genes contains two catabolite-responsive elements (cre1 and cre2) that can be bound by CcpA. Notably, the cre2 site of ackA overlaps with a CodY-binding site. The CcpA- and CodY-binding sites in the promoter region of both genes were further defined by site-directed mutagenesis. Some differences between the reported consensus CodY binding site and the region protected by S. mutans CodY were noted. Transcription of the pta and ackA genes in the ccpA mutant strain was markedly different at low pH relative to transcription at neutral pH. Thus, CcpA and CodY are direct regulators of transcription of ackA and pta in S. mutans that optimize acetate metabolism in response to carbohydrate, amino acid availability, and environmental pH.IMPORTANCE The human dental caries pathogen Streptococcus mutans is remarkably adept at coping with extended periods of carbohydrate limitation during fasting periods. The phosphotransacetylase-acetate kinase (Pta-Ack) pathway in S. mutans modulates carbohydrate flux and fine-tunes the ability of the organisms to cope with stressors that are commonly encountered in the oral cavity. Here, we show that CcpA controls transcription of the pta and ackA genes via direct interaction with the promoter regions of both genes and that branched-chain amino acids (BCAAs), particularly isoleucine, enhance the ability of CodY to bind to the promoter region of the ackA gene. A working model is proposed to explain how regulation of pta and ackA genes by these allosterically controlled regulatory proteins facilitates proper carbon flow and energy production, which are essential functions during infection and pathogenesis as carbohydrate and amino acid availability continually fluctuate.

Dataset Information

Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans.

Publications

Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans.

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