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

The synthesis of acetylornithine delta-transaminase is induced by arginine and by rifampin in an arginine-inducible mutant of Escherichia coli W. A mutant of the arginine-inducible strain was isolated which is resistant to rifampin. The mutation which has brought about rifampin resistance has altered RNA polymerase and has simultaneously altered the regulation of arginine biosynthesis. Three of the enzymes of arginine biosynthesis, acetylornithinase, ornithine transcarbamylase, and argininosuccinase, show a greater rate of derepression and a 2--12-fold higher level of enzyme activity in the rifampin-resistant mutant than in the parent arginine-inducible strain. Acetylornithine delta-transaminase is no longer inducible by rifampin alone, and the level of inducibility by arginine plus rifampin has been reduced by 70%. The results indicate that RNA polymerase is involved in regulation of arginine biosynthesis in E. coli W.
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PMID:Alteration of regulation of arginine biosynthesis in Escherichia coli W by mutation to rifampin resistance. 109 Dec 97

Cell extracts from Escherichia coli were used to study both transcription and coupled translation of the argECBH gene cluster. Argininosuccinase (the argH enzyme) and N-acetylornithinase (the argE enzyme) were synthesized for 90 to 120 min, and hybridizable argECBH mRNA was synthesized for 60 min after the addition of a lambda or phi 80 dargECBH DNA template. L-Arginine (2.5 mM) repressed synthesis by argR+ extracts of argECBH mRNA 2-, to 3-fold, argE enzyme 5- to 8-fold, and argH enzyme 20- to 60-fold. Repression was specific for L-arginine, and argR extracts were insensitive to added L-arginine. The argECBH mRNA made under conditions of restricted protein synthesis had reduced ability to function in the formation of the argE and argH enzymes and was found to be predominantly 6 to 8S in sucrose density gradients. When protein synthesis was allowed, the mRNA formed was functional, and large amounts of 14 to 23S argECBH mRNA appeared on sucrose gradients. An S-100 supernatant freed of ribosomes was capable of producing hybridizable arg mRNA, but significant functional message was only produced when ribosomes were present. When purified RNA polymerase was used, the formation of short 6 to 8S argECBH mRNA was dependent upon added rho protein. The data suggest that rho-dependent sites in the argECBH operon allow early termination of mRNA synthesis when transcription is not coupled to active enzyme synthesis.
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PMID:Regulation and coupling of argECBH mRNA and enzyme synthesis in cell extracts of Escherichia coli. 637 85