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)

Expression of the Vibrio fischeri luminescence genes (luxR and luxICDABEG) in Escherichia coli requires autoinducer (N-3-oxohexanoyl homoserine lactone) and LuxR protein, which activate transcription of luxICDABEG (genes for autoinducer synthase and the luminescence enzymes), and cyclic AMP (cAMP) and cAMP receptor protein (CRP), which activate transcription of the divergently expressed luxR gene. In E. coli and in V. fischeri, the autoinducer-LuxR protein-dependent induction of luxICDABEG transcription (called autoinduction) is delayed by glucose, whereas it is promoted by iron restriction, but the mechanisms for these effects are not clear. To examine in V. fischeri control of lux gene expression by autoinducer, cAMP, glucose, and iron, lux::Mu dI(lacZ) and lux deletion mutants of V. fischeri were constructed by conjugation and gene replacement procedures. beta-Galactosidase synthesis in a luxC::lacZ mutant exhibited autoinduction. In a luxR::lacZ mutant, complementation by the luxR gene was necessary for luminescence, and addition of cAMP increased beta-galactosidase activity four- to sixfold. Furthermore, a luxI::lacZ mutant produced no detectable autoinducer but responded to its addition with induced synthesis of beta-galactosidase. These results confirm in V. fischeri key features of lux gene regulation derived from studies with E. coli. However, beta-galactosidase specific activity in the luxI::lacZ mutant, without added autoinducer, exhibited an eight- to tenfold decrease and rise back during growth, as did beta-galactosidase and luciferase specific activities in the luxR::lacZ mutant and luciferase specific activity in a delta(luxR luxICD) mutant. The presence of glucose delayed the rise back in beta-galactosidase and luciferase specific activities in these strains, whereas iron restriction promoted it. Thus, in addition to transcriptional control by autoinducer and LuxR protein, the V. fischeri lux system exhibits a cell density-dependent modulation of expression that does not require autoinducer, LuxR protein, or known lux regulatory sites. The response of autoinducer-LuxR protein-independent modulation to glucose and iron may account for how these environmental factors control lux gene expressions.
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PMID:Cell density-dependent modulation of the Vibrio fischeri luminescence system in the absence of autoinducer and LuxR protein. 131 12

In Pseudomonas aeruginosa, the transcriptional activator LasR and the Pseudomonas autoinducer PAI, are necessary for efficient transcriptional activation of the lasB gene, encoding elastase (L. Passador, J. M. Cook, M.J. Gambello, L. Rust, and B. H. Iglewski, Science 260:1127-1130, 1993). The transcriptional start points of lasI in Escherichia coli and P. aeruginosa were determined by S1 nuclease mapping. In the presence of both LasR and PAI, the start site, T1, is located at position -25 relative to the ATG translational start codon. A minor transcriptional start, T2, is found at position -13 when lasI is transcribed in the absence of either LasR or PAI in P. aeruginosa and E. coli, respectively. To begin to closely examine the regulation of lasI, whose product is involved in the synthesis of PAI, a lasI-lacZ fusion on a lambda phage was constructed to form monolysogens of E. coli MG4. Lysogens supplied only with either lasI or lasR via multicopy plasmids demonstrated no significant increase in beta-galactosidase expression compared with control levels. Lysogens in which both lasR and lasI were supplied in multicopy exhibited a 62-fold increase in expression, and a lysogen in which lasR was supplied in trans and which was grown in the presence of exogenous PAI exhibited a 60-fold increase. Thus, LasR and PAI are necessary for the full expression of lasI in E. coli. The interchangeability of the P. aeruginosa and Vibrio fischeri homologs LasR and LuxR and their respective autoinducers, PAI and VAI, as activators of lasI-lacZ was examined. Only the combination of LasR and PAI significantly increased the expression of lasI. The comparison of lasI-lacZ and lasB-lacZ expression lysogens grown in the presence of lasR and PAI revealed that half-maximal expression of lasI required 0.1 nM PAI, in contrast to the 1.0 nM PAI necessary for lasB half-maximal expression. These results suggest an autoinduction regulatory hierarchy in which LasR and low PAI concentrations primarily activate lasI expression in a regulatory loop. With the accumulation of PAI, secondary activation of virulence product genes such as lasB occurs.
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PMID:Activation of the Pseudomonas aeruginosa lasI gene by LasR and the Pseudomonas autoinducer PAI: an autoinduction regulatory hierarchy. 783 99

The lasR gene of Pseudomonas aeruginosa is required for transcription of the genes for elastase (lasB) and LasA protease (lasA), two proteases associated with virulence. We report here that the alkaline protease gene (apr) also requires the lasR gene for transcription. Alkaline protease mRNA was absent in the lasR mutant PAO-R1 and present when an intact lasR gene was supplied in trans as determined by Northern (RNA) analysis. The lasR gene also enhances exotoxin A production. Exotoxin A activity in supernatants of PAO-R1 were 30% less than in supernatants of the parental strain, PAO-SR. Multiple copies of lasR in trans in PAO-R1 in increased toxin A activity to twice the parental levels. Analysis of PAO-R1 containing the toxA promoter fused to beta-galactosidase suggests that LasR acts at the toxA promoter or at upstream toxA mRNA sequences. beta-Galactosidase activity was approximately 40% lower in PAO-R1 than in the parental strain, PAO-SR. Furthermore, the effect of LasR on the toxA promoter is not due to the stimulation of transcription of regA, a transcriptional activator of toxA. No difference in chloramphenicol acetyltransferase (CAT) activity was noted between PAO-SR and PAO-R1 containing transcriptional regA promoter-CAT gene fusions. These results broaden the regulatory dominion of lasR and suggest that the lasR gene plays a global role in P. aeruginosa pathogenesis.
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PMID:LasR of Pseudomonas aeruginosa is a transcriptional activator of the alkaline protease gene (apr) and an enhancer of exotoxin A expression. 845 22

A series of structural analogs of the Pseudomonas aeruginosa autoinducer [PAI, N-3-oxo-dodecanoyl homoserine lactone] were obtained and tested for their ability to act as autoinducers in stimulating the expression of the gene for elastase (lasB) by measuring beta-galactosidase production from a lasB-lacZ gene fusion in the presence of the transcriptional activator LasR. The data suggest that the length of the acyl side chain of the autoinducer molecule is the most critical factor for activity. Replacement of the ring O by S in the homoserine lactone moiety can be tolerated. Tritium-labelled PAI ([3H]PAI) was synthesized and used to demonstrate the association of [3H]PAI with cells overexpressing LasR. The PAI analogs were also tested for their ability to compete with [3H]PAI for binding of LasR. Results from the competition assays suggest that once again the length of the acyl side chain appears to be crucial for antagonist activity. The presence of the 3-oxo moiety also plays a significant role in binding since analogs which lacked this moiety were much less effective in blocking binding of [3H]PAI. All analogs demonstrating competition with PAI in binding to LasR also exhibited the ability to activate lasB expression, suggesting that they are functional analogs of PAI.
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PMID:Functional analysis of the Pseudomonas aeruginosa autoinducer PAI. 883 Jun 97

The root-associated biological control bacterium Pseudomonas aureofaciens 30-84 produces a range of exoproducts, including protease and phenazines. Phenazine antibiotic biosynthesis by phzXYFABCD is regulated in part by the PhzR-PhzI quorum-sensing system. Mutants defective in phzR or phzI produce very low levels of phenazines but wild-type levels of exoprotease. In the present study, a second genomic region of strain 30-84 was identified that, when present in trans, increased beta-galactosidase activity in a genomic phzB::lacZ reporter and partially restored phenazine production to a phzR mutant. Sequence analysis identified two adjacent genes, csaR and csaI, that encode members of the LuxR-LuxI family of regulatory proteins. No putative promoter region is present upstream of the csaI start codon and no lux box-like element was found in either the csaR promoter or the 30-bp intergenic region between csaR and csaI. Both the PhzR-PhzI and CsaR-CsaI systems are regulated by the GacS-GacA two-component regulatory system. In contrast to the multicopy effects of csaR and csaI in trans, a genomic csaR mutant (30-84R2) and a csaI mutant (30-84I2) did not exhibit altered phenazine production in vitro or in situ, indicating that the CsaR-CsaI system is not involved in phenazine regulation in strain 30-84. Both mutants also produced wild-type levels of protease. However, disruption of both csaI and phzI or both csaR and phzR eliminated both phenazine and protease production completely. Thus, the two quorum-sensing systems do not interact for phenazine regulation but do interact for protease regulation. Additionally, the CsaI N-acylhomoserine lactone (AHL) signal was not recognized by the phenazine AHL reporter 30-84I/Z but was recognized by the AHL reporters Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136(pCF240). Inactivation of csaR resulted in a smooth mucoid colony phenotype and formation of cell aggregates in broth, suggesting that CsaR is involved in regulating biosynthesis of cell surface components. Strain 30-84I/I2 exhibited mucoid colony and clumping phenotypes similar to those of 30-84R2. Both phenotypes were reversed by complementation with csaR-csaI or by the addition of the CsaI AHL signal. Both quorum-sensing systems play a role in colonization by strain 30-84. Whereas loss of PhzR resulted in a 6.6-fold decrease in colonization by strain 30-84 on wheat roots in natural soil, a phzR csaR double mutant resulted in a 47-fold decrease. These data suggest that gene(s) regulated by the CsaR-CsaI system also plays a role in the rhizosphere competence of P. aureofaciens 30-84.
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PMID:A second quorum-sensing system regulates cell surface properties but not phenazine antibiotic production in Pseudomonas aureofaciens. 1152 37

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic lung infections in cystic fibrosis patients and is a major source of nosocomial infections. This bacterium controls many virulence factors by using two quorum-sensing systems, las and rhl. The las system is composed of the LasR regulator protein and its cell-to-cell signal, N-(3-oxododecanoyl) homoserine lactone, and the rhl system is composed of RhlR and the signal N-butyryl homoserine lactone. A third intercellular signal, the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4-quinolone), also regulates numerous virulence factors. PQS synthesis requires the expression of multiple operons, one of which is pqsABCDE. Previous experiments showed that the transcription of this operon, and therefore PQS production, is negatively regulated by the rhl quorum-sensing system and positively regulated by the las quorum-sensing system and PqsR (also known as MvfR), a LysR-type transcriptional regulator protein. With the use of DNA mobility shift assays and beta-galactosidase reporter fusions, we have studied the regulation of pqsR and its relationship to pqsA, lasR, and rhlR. We show that PqsR binds the promoter of pqsA and that this binding increases dramatically in the presence of PQS, implying that PQS acts as a coinducer for PqsR. We have also mapped the transcriptional start site for pqsR and found that the transcription of pqsR is positively regulated by lasR and negatively regulated by rhlR. These results suggest that a regulatory chain occurs where pqsR is under the control of LasR and RhlR and where PqsR in turn controls pqsABCDE, which is required for the production of PQS.
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PMID:Regulation of Pseudomonas quinolone signal synthesis in Pseudomonas aeruginosa. 1596 46

A pyocyanin overproducer with insertional inactivation of ptsP gene was isolated from a mini-Mu insertion library in Pseudomonas aeruginosa PA68. The mutation was complemented by a functional ptsP gene in trans. The pyocyanin-overproducing phenotype was also found in a ptsP mutant constructed by gene replacement in the P. aeruginosa PAO1 strain. Reporter plasmids with P(qscR)-lacZ, P(lasI)-lacZ and P(rhlI)-lacZ were constructed and the beta-galactosidase activity in the ptsP mutant/wild-type background was measured. The results showed that lack of Enzyme I(Ntr) (EI(Ntr), encoded by ptsP) decreased transcription from the P(qscR) promoter and increased the activity of the P(lasI) and P(rhlI) promoters. Normally, QscR represses the quorum-sensing LasR-LasI and RhlR-RhlI systems involved in pyocyanin regulation. Our results showed that the ptsP gene has an important role in the regulation of pyocyanin production and that two quorum-sensing systems and their repressor QscR are involved in this regulation.
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PMID:Influence of ptsP gene on pyocyanin production in Pseudomonas aeruginosa. 1623 83