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)

In Pseudomonas aeruginosa, production of exotoxin A, an ADP-ribosyltransferase, is a complex and highly regulated process. Two positively acting regulatory genes, regA and regB, have been cloned and characterized. To identify additional exotoxin A regulatory genes, we have characterized four N-methyl-N'-nitro-N-nitrosoguanidine-generated mutants of P. aeruginosa PA103 which are deficient in exotoxin A production. These mutants (PA103-8, PA103-15, PA103-16, and PA103-19) do not accumulate intracellular exotoxin A and are not complemented by the cloned toxA or regAB genes. This observation indicates that the lesion(s) in the mutants is probably in an exotoxin A regulatory gene(s) and is not in the genes for secretion of exotoxin A or in the toxA or regAB genes. To assess the effect of the putative regulatory mutations on the toxA and regAB genes, we compared the activity of the toxA and regAB promoters in the mutant and parental strains using plasmids containing the genes for beta-galactosidase or chloramphenicol acetyltransferase under the control of either the toxA or the regAB promoter. The toxA promoter-beta-galactosidase fusion plasmid could not be maintained in PA103-8. beta-Galactosidase expression driven by the toxA promoter was absent in the mutant PA103-19 and occurred at a low level, which was not repressed by iron in mutants PA103-15 and PA103-16. The regAB genes are temporally controlled by two promoters, P1 and P2. In all four mutants, regAB P1 promoter activity was reduced; however, expression under the control of the regAB P2 promoter was normal. These observations suggest the existence of one or more regulatory genes which directly affect expression of both the toxA and the regAB P1 promoters.
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PMID:Characterization of Pseudomonas aeruginosa mutants that are deficient in exotoxin A synthesis and are altered in expression of regA, a positive regulator of exotoxin A. 811 61

From Azospirillum lipoferum (Al) FS, a nitrogen-fixing bacterium isolated from the rhizosphere of rice, we cloned and sequenced draT, encoding dinitrogenase reductase ADP-ribosyltransferase, and draG, encoding dinitrogenase reductase-activating glycohydrolase. The nucleotide sequences of draTG showed extensive similarity to the same genes from Azospirillum brasilense, Rhodospirillum rubrum and Rhodobacter capsulatus, and they are assumed to be co-transcribed as a single operon. When this draTG operon was introduced into Klebsiella oxytoca, this organism acquired the ability to respond to extracellular NH(+4) ions with reversible inhibition of nitrogenase activity, similar to that seen in Al FS. We constructed a plasmid containing a draT::lacZ gene fusion and found that beta-galactosidase activity was detected under microaerobic conditions, regardless of NH(+4) concentration, but not under aerobic conditions. This indicates that the transcription of draTG responds to the level of oxygen, but not to that of NH(+4) ions.
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PMID:Cloning, sequencing and transcriptional regulation of the draT and draG genes of Azospirillum lipoferum FS. 862 Oct 68