Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated promoters inducible by paraquat, a superoxide radical-generating agent, from Escherichia coli, using promoter-probing plasmid pJAC4 (Y.S. Koh and J.H. Roe, Korean J. Microbiol. 31:267-273, 1993). One promoter clone pqi-5 (pqi denotes paraquat-inducible gene) was mapped at 21.8 min on the E. coli chromosome by using the Kohara phage library. We constructed an operon fusion of the lacZ gene with the pqi-5 promoter to monitor the expression of the gene in the single-copy state. LacZ expression was induced about 7- to 13-fold by 77 to 780 microM paraquat. Other known superoxide generators such as menadione, phenazine methosulfate, and plumbagin also induced the expression of beta-galactosidase in this fusion strain. On the other hand, no significant induction was observed with treatment with hydrogen peroxide, ethanol, and heat shock. Induction of beta-galactosidase was significantly reduced by introducing a delta sox-8::cat or soxS3::Tn10 mutation into the fusion strain, indicating that pqi-5 is a member of the soxRS regulon. A DNA fragment containing the pqi-5 promoter was cloned and sequenced from the Kohara phage E2E5. We identified two pqi-5 open reading frames (ORFs); ORF-A encodes a predicted protein of 342 amino acids, and ORF-B is truncated at the cloning site. The transcription start site from the pqi-5 promoter was determined by primer extension and S1 nuclease protection analyses. Northern (RNA) and S1 analyses indicated that there are two kinds of pqi-5 transcript; one covers ORF-A only and the other covers ORF-A and possibly also ORF-B.
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PMID:Isolation of a novel paraquat-inducible (pqi) gene regulated by the soxRS locus in Escherichia coli. 775 Dec 75

We isolated a promoter that is inducible by paraquat, a superoxide-generating agent, from Escherichia coli using the promoter-probe plasmid pRS415. Sequence analysis revealed that the promoter derives from the ribA gene encoding GTP cyclohydrolase II, which is the first enzyme in the biosynthetic pathway of riboflavin. We fused the lacZ gene with the ribA promoter to monitor the expression of the gene in the single-copy state. LacZ expression from the ribA promoter was induced about eight-fold by 200 microM paraquat. Other known superoxide generators, menadione and plumbagin, also induced the expression of beta-galactosidase in the fusion strain. On the other hand, no significant induction was observed following treatment with hydrogen peroxide, ethanol or heat shock. Induction of beta-galactosidase was significantly reduced by the introduction of a delta sox-8::cat or soxS3::Tn10 mutation into the fusion strain, indicating that the ribA gene is a member of the soxRS regulon. The transcriptional start site was determined by primer extension analysis and putative binding sites for SoxS in both orientations were identified. GTP cyclohydrolase II activity in soluble extracts of E. coli increased more than three-fold on treatment with paraquat. This increase was dependent on the soxRS locus, and reflects the increase in transcript levels. However, flavin pools did not change significantly. A possible role for ribA induction during superoxide stress is discussed.
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PMID:Regulation of the ribA gene encoding GTP cyclohydrolase II by the soxRS locus in Escherichia coli. 870 66