Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleotide sequence of the upstream region of the aspartate kinase genes of Thermus thermophilus HB27 revealed the presence of two open reading frames in the orientation opposite to that of the aspartate kinase genes. The upstream open reading frame termed ORF375 encodes a protein composed of 375 amino acid residues, possessing amino acid sequence motifs for methylases. Another open reading frame designated as sigA encodes a protein of 423 amino acid residues which shows significant identity in amino acid sequence to the principal sigma factor, a component of the DNA-dependent RNA polymerase holoenzyme. The close proximity of the open reading frames suggested that the two genes are transcribed in a polycistronic manner. By the use of an Escherichia coli expression system, SigA was produced in a soluble form. An in vitro transcription assay of purified SigA reconstituted with the core RNA polymerase of E. coli showed that Thermus SigA functioned as a sigma factor to initiate specific transcription.
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PMID:Cloning and characterization in Escherichia coli of the gene encoding the principal sigma factor of an extreme thermophile, Thermus thermophilus. 1018 47

The threonine dehydratase IlvA is part of the isoleucine biosynthesis pathway in the Gram-positive model bacterium Bacillus subtilis. Consequently, deletion of ilvA causes isoleucine auxotrophy. It has been reported that ilvA pseudo-revertants having a derepressed hom-thrCB operon appear in the presence of threonine. Here we have characterized two classes of ilvA pseudo-revertants. In the first class the hom-thrCB operon was derepressed unmasking the threonine dehydratase activity of the threonine synthase ThrC. In the second class of mutants, threonine biosynthesis was more broadly affected. The first class of ilvA pseudo-revertants had a mutation in the Phom promoter (P*hom ), resulting in constitutive expression of the hom-thrCB operon. In the second class of ilvA pseudo-revertants, the thrR gene encoding a putative DNA-binding protein was inactivated, also resulting in constitutive expression of the hom-thrCB operon. Here we demonstrate that ThrR is indeed a DNA-binding transcription factor that regulates the hom-thrCB operon and the thrD aspartokinase gene. DNA binding assays uncovered the DNA-binding site of ThrR and revealed that the repressor competes with the RNA polymerase for DNA binding. This study also revealed that ThrR orthologs are ubiquitous in genomes from the Gram-positive phylum Firmicutes and in some Gram-negative bacteria.
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PMID:ThrR, a DNA-binding transcription factor involved in controlling threonine biosynthesis in Bacillus subtilis. 2726 Jun 60