Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D03345 (beta-Galactosidase)
 434 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA-dependent synthesis of beta-galactosidase was optimized in extracts made from cells lysed by a standard French pressure cell. Extracts made at 3200 psi synthesized up to 25-fold more beta-galactosidase than extracts made at 7500 psi. beta-Galactosidase synthesis was cyclic 3', 5' AMP dependent, as expected, and in optimal conditions transcription and translation proceeded at 8.6 nucleotides and 2.7 amino acids per s, respectively. The high pressure extracts were stimulated 3- to 5-fold by Ca2+, especially at low Mg2+ concentrations. In contrast, extracts prepared at low pressure were inhibited as much as 50-fold by Ca2+ ions. The inhibition by Ca2+ was analyzed further. Addition of kasugamycin, an antibiotic that acts on ribosomes, to reactions containing Ca2+ stimulated beta-galactosidase synthesis to nearly control levels. Extracts from a kasugamycin resistant mutant were neither inhibited by Ca2+ nor stimulated by the addition of kasugamycin to in vitro reactions containing Ca2+. The change in the mutant was ascribed to the ribosomes by testing combinations of soluble proteins, ribosome wash, and ribosomes from parental and mutant strains. These results suggest that Ca2+ ions inhibit translation by ribosomes, very likely at an initiation step; and that they enhance enzyme synthesis only in conditions where translation is inefficient (high-pressure extracts at low concentrations of Mg2+, for example). This latter effect is probably a consequence of increased RNA stability in the presence of Ca2+ (Cremer, K., and Schlessinger, D. (1974), J. Biol. Chem. 249,4730).
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PMID:Escherichia coli DNA-directed beta-galactosidase synthesis in presence and absence of Ca2+. 32 Oct 10

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

The Escherichia coli rhaSR operon encodes two AraC family transcription activators, RhaS and RhaR, and is activated by RhaR in the presence of L-rhamnose. beta-Galactosidase assays of various rhaS-lacZ promoter fusions combined with mobility shift assays indicated that a cyclic AMP receptor protein (CRP) site located at -111.5 is also required for full activation of rhaSR expression. To address the mechanisms of activation by CRP and the RNA polymerase alpha-subunit C-terminal domain (alpha-CTD) at rhaSR, we tested the effects of alanine substitutions in CRP activating regions 1 and 2, overexpression of a truncated version of alpha (alpha-Delta235), and alanine substitutions throughout alpha-CTD. We found that DNA-contacting residues in alpha-CTD are required for full activation, and for simplicity, we discuss alpha-CTD as a third activator of rhaSR. CRP and RhaR could each partially activate transcription in the absence of the other two activators, and alpha-CTD was not capable of activation alone. In the case of CRP, this suggests that this activation involves neither an alpha-CTD interaction nor cooperative binding with RhaR, while in the case of RhaR, this suggests the likelihood of direct interactions with core RNA polymerase. We also found that CRP, RhaR, and alpha-CTD each have synergistic effects on activation by the others, suggesting direct or indirect interactions among all three. We have some evidence that the alpha-CTD-CRP and alpha-CTD-RhaR interactions might be direct. The magnitude of the synergistic effects was usually greater with just two activators than with all three, suggesting possible redundancies in the mechanisms of activation by CRP, alpha-CTD, and RhaR.
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PMID:Interdependence of activation at rhaSR by cyclic AMP receptor protein, the RNA polymerase alpha subunit C-terminal domain, and rhaR. 1107 23

We describe a fast, simple assay for testing ligands for binding to an unknown receptor after transfection of that receptor cDNA into tissue culture cells. The assay is based on a mouse L cell line (LVIP2.OZc) that contains a cyclic AMP responsive reporter construct and is performed in 96-well plates. If the appropriate agonist binds to a receptor clone coupled to G(s) proteins, activation of adenylyl cyclase produces cAMP which in turn induces the enzyme beta-galactosidase in LVIP2.0Zc cells. beta-Galactosidase activity is detected by staining cells with a chromogenic substrate. After cell lysis, incubation with o-nitrophenyl beta-d-galactopyranoside (ONPG) results in a yellow color. Color development can be observed with the naked eye or read with a plate reader at 405 nm. Agonists that bind to G(i)-coupled receptors can be identified by inhibition of forskolin-induced expression of beta-galactosidase.
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PMID:Method for identifying ligands that bind to cloned G(s)- or G(i)-coupled receptors. 1991 16