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)

L-Aspartase was purified from Bacillus subtilis, its N-terminal amino acid sequence was determined to construct a probe for the aspartase gene, and the gene (termed ansB) was cloned and sequenced. A second gene (termed ansA) was found upstream of the ansB gene and coded for L-asparaginase. These two genes were in an operon designated the ans operon, which is 80% cotransformed with the previously mapped aspH1 mutation at 215 degrees. Primer extension analysis of in vivo ans mRNA revealed two transcription start sites, depending on the growth medium. In wild-type cells in log-phase growth in 2x YT medium (tryptone-yeast extract rich medium), the ans transcript began at -67 relative to the translation start site, while cells in log-phase growth or sporulating (t1 to t4) in 2x SG medium (glucose nutrient broth-based moderately rich medium) had an ans transcript which began at -73. The level of the -67 transcript was greatly increased in an aspH mutant grown in 2x YT medium; the -67 transcript also predominated when this mutant was grown in 2x SG medium, although the -73 transcript was also present. In vitro transcription of the ans operon by RNA polymerase from log-phase cells grown in 2x YT medium and log-phase or sporulating cells grown in 2x SG medium yielded only the -67 transcript. Depending on the growth medium, the levels of asparaginase and aspartase were from 2- to 40-fold higher in an aspH mutant than in wild-type cells, and evidence was obtained indicating that the gene defined by the aspH1 mutation codes for a trans-acting transcriptional regulatory factor. In wild-type cells grown in 2x SG medium, the levels of both aspartase and asparaginase decreased significantly by t0 of sporulation but then showed a small increase, which was mirrored by changes in the level of beta-galactosidase from an ansB-lacZ fusion. The increase in the activities of ans operon enzymes between t2 and t5 of sporulation was found primarily in the forespore, and the great majority of the increased was found in the mature spore. However, throughout sporulation the only ans transcript detected was the -73 form, and no sporulation-specific RNA polymerase tested yielded a -73 transcript in vitro.
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PMID:Cloning, nucleotide sequence, and expression of the Bacillus subtilis ans operon, which codes for L-asparaginase and L-aspartase. 171 Oct 29

Previous work has shown that expression of the Bacillus subtilis ans operon which codes for L-asparaginase and L-aspartase, is both increased and made insensitive to repression by NH4+ by the aspH1 mutation. In current work, the gene in which the aspH1 mutation resides has been identified and sequenced; this gene, termed ansR, is immediately upstream of, but transcribed in the opposite direction from, the ans operon. The promoter region of ansR contains -10 and -35 sequences similar to those recognized by RNA polymerase containing the major vegetative-cell sigma factor sigma A, and ansR appears to be monocistronic. The ansR gene codes for a 116-residue protein, but the aspH1 mutant allele has an additional guanine residue at codon 55, resulting in generation of a truncated polypeptide of only 58 residues. Insertional inactivation of ansR resulted in a phenotype identical to that of the aspH1 mutant. The predicted amino acid sequence of the ansR gene product (AnsR) was homologous to that of the repressor of B. subtilis prophage PBSX, and a helix-turn-helix motif, characteristic of many DNA-binding proteins, was present in the AnsR amino-terminal region. These results suggest that ansR codes for a repressor of the ans operon.
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PMID:Cloning and nucleotide sequence of the Bacillus subtilis ansR gene, which encodes a repressor of the ans operon coding for L-asparaginase and L-aspartase. 847 18

Regular blood transfusion puts beta-thalassemia major patients at a higher risk of developing hepatic iron overload and hepatitis C virus (HCV) infection. The association between several transfusion-related factors and an increased risk of developing HCV viremia has been reported. The effect of HCV infection on liver damage in transfusion-dependent thalassemia patients has been poorly described. A sample of 100 Egyptian transfusion-dependent beta-thalassemia major children were studied. Individual patients underwent full history taking, clinical examination and a panel of laboratory tests including HCV ribonucleic acid polymerase chain reaction (HCV-PCR) in blood samples. Liver biopsy was performed for 24 patients. HCV-PCR was positive in 64% of patients. A statistically significant correlation was found between HCV-PCR positivity (HCV viremia) and shorter inter-transfusion interval. There was a significant positive correlation between mean serum ferritin level and mean levels of alanine aminotransferase and aspartase aminotransferase. Histopathologic features of both chronic hepatitis and siderosis were present in 91.7% of biopsy specimens, and fibrosis was present in 41.67%. A higher risk of HCV viremia is noted with a shorter inter-transfusion interval. The reduced role of HCV infection in chronic liver injury in this group of patients may be surpassed by the associated effects of iron overload because of the chronic transfusion. However, the latter finding should be verified in larger studies.
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PMID:Clinicovirologic analysis of hepatitis C infection in transfusion-dependent beta-thalassemia major children. 1938 13