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)

Translation of mitochondrial cytochrome b RNA in yeast requires the product of the nuclear gene CBS1, a 27.5 kDa soluble mitochondrial protein. In this paper we show that the CBS1 gene is located on chromosome IV immediately adjacent to COX9, the gene coding for cytochrome c oxidase subunit VIIa. CBS1 is transcribed as a very low abundant 900 b RNA. Transcription starts at a single position 101 bp upstream of the CBS1 initiation codon. At positions -39 to -27 of its leader sequence it contains a small open reading frame of 4 codons. By monitoring the beta-galactosidase activity of a CBS1/lacZ fusion construct we show that expression of CBS1 is subjected to regulation by oxygen and by glucose: the beta-galactosidase activity is elevated threefold in glycerol or galactose grown cells compared to that in glucose grown cells. A further threefold reduction of the activity is observed in anaerobically grown cells. In accordance with this result is the observation that the steady-state level of CBS1 mRNA of anaerobically grown cells is ninefold lower than that of aerobically cultured cells.
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PMID:Chromosomal localization and expression of CBS1, a translational activator of cytochrome b in yeast. 255 Jul 65

A number of bacterial isolates which could not be identified as either Salmonella or Citrobacter by conventional biochemical tests and could not be typed as Salmonella with available antisera, were further examined biochemically and by lysis with phage Felix 0.1. Glycerol-positive salmonellae and lysine-positive citrobacters were encountered, which could be confused with the other genus, but when the reactions of such strains were examined in the other tests, accurate identifications could be done. Of the tests examined, glycerol fermentation, the beta-galactosidase test, lysine decarboxylation, sorbose fermentation, galacturonate fermentation and lysis by the phage could be used in the differentiation. These tests in combination, rather than 1 or 2 single tests gave reliable and conclusive differentiation.
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PMID:The biochemical differentiation between Salmonella and Citrobacter. 269 17

Escherichia coli and Salmonella typhimurium preferentially utilize sugar substrates of the phosphoenol-pyruvate:glycose phosphotransferase system (PTS) when the growth medium also contains other sugars. This phenomenon, diauxic growth, is regulated by the crr gene, which encodes the PTS protein IIIGlc (Saffen, D.W., Presper, K.A., Doering, T.L., and Roseman, S. (1987) J. Biol. Chem. 16241-16253). We have proposed that non-PTS permeases are regulated by their interaction with IIIGlc, and in vitro studies from other laboratories have provided support for this model, but the in vivo effects of excess IIIGlc are not known. In the present studies, transformed cells that overproduced IIIGlc 2- and 10-fold, respectively, were constructed from a pts+ strain of E. coli and plasmids containing the crr gene. In the 2-fold overproducer, fermentation of, and growth on the non-PTS carbohydrates glycerol, lactose, maltose, and melibiose was generally more sensitive to the glucose analogue methyl-alpha-D-glucopyranoside than in a control strain containing normal levels of IIIGlc. In addition, inhibition of lactose permease activity by methyl-alpha-glucoside (inducer exclusion) was more effective in the 2-fold overproducer than in the control strain, particularly when the permease activity was high. The 10-fold IIIGlc overproducing strain had a requirement for the amino acids methionine, isoleucine, leucine, and valine that may or may not be related to the increased concentration of IIIGlc. Fermentation of non-PTS carbohydrates was also poor in the latter strain. Finally, lactose permease activity was 50% of that in control cells containing the same levels of beta-galactosidase, and the lactose permease activity in the IIIGlc overproducer was reduced to an extremely low level in the presence of methyl alpha-glucoside. Thus there is an inverse relationship between the cellular concentration of IIIGlc and the ability to metabolize non-PTS substrates. The results are consistent with the model where inducer exclusion is affected by a direct interaction between IIIGlc and a non-PTS transport system.
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PMID:Sugar transport by the bacterial phosphotransferase system. In vivo regulation of lactose transport in Escherichia coli by IIIGlc, a protein of the phosphoenolpyruvate:glycose phosphotransferase system. 282 84

In order to study the regulation of expression of the iso2-cytochrome c gene, we have constructed a fused gene between the 5'flanking region of the gene coding for the yeast iso2-cytochrome c and the coding region of the E. coli beta-galactosidase lacZ gene. When introduced in yeast cells this hybrid gene is expressed and regulated like the production of iso2-cytochrome c: it is under the control of the general catabolic repression and of the unlinked trans-acting CYP1 gene whose CYP1-18 allele causes an overproduction of iso2-cytochrome c. The expression of hybrid genes whose upstream region has been progressively shortened or altered by internal deletions was studied either in wild-type CYP1+ cells or in cells carrying the CYP1-18 allele grown either on glucose or on glycerol. It appears that the expression and the regulation of the iso2-cytochrome c gene is controlled by an upstream regulatory site composed of a positive and a negative element. This site is the target of regulation by the CYP1 gene product and, directly or through this gene, of the control by the general catabolic repression.
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PMID:Localization of the upstream regulatory sites of yeast iso2-cytochrome c gene. 298 43

In this study, we investigated the relationship between carbohydrate metabolism and repression of staphylococcus enterotoxin A (SEA) in Staphylococcus aureus 196E and a pleiotrophic mutant derived from strain 196E. The mutant, designated at strain 196E-MA, lacked a functional phosphoenolpyruvate phosphotransferase system (PTS). The mutant produced acid, under aerobic conditions, from only glucose and glycerol. The parent strain contained an active PTS, and aerobically produced acid from a large number of carbohydrates. Prior growth in glucose led to repression of SEA synthesis in the parent strain; addition to the casamino acids enterotoxin production medium (CAS) led to more severe repression of toxin synthesis. The repression was not related to pH decreases produced by glucose metabolism. When S. aureus 196E was grown in the absence of glucose, there was inhibition of toxin production as glucose level was increased in CAS. The inhibition was related to pH decrease and was unlike the repression observed with glucose-grown strain 196E. The inhibition of SEA synthesis in mutant strain 196E-MA was approximately the same in cells grown with or without glucose and was pH related. Repression of SEA synthesis similar to that seen with glucose-grown S. aureus 196E could not be demonstrated in the mutant. In addition, glucose-grown S. aureus 196E neither synthesized beta-galactosidase nor showed respiratory activity with certain tricarboxylic acid (TCA) cycle compounds. Glucose-grown strain 196E-MA, however, did not show suppressed respiration of TCA cycle compounds; beta-galactosidase was not synthesized because the mutant lacked a functional PTS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enterotoxin A production in Staphylococcus aureus: inhibition by glucose. 301 14

Titrimetric addition of hypochlorous acid (HOCl) or chloramine (NH2Cl) to suspensions of Escherichia coli decreases their ability to accumulate 14C-labeled glutamine, proline, thiomethylgalactoside, and leucine in a manner that approximately coincides with loss of cell viability; quantitative differences in cellular response are observed with the two oxidants. Inhibition of beta-galactosidase activity in E. coli ML-35, a strain lacking functional lactose permease, is complex and also depends upon the identity of the oxidant. Membrane proton conductivities and glycerol permeabilities are unchanged by addition of HOCl or NH2Cl in excess of that required for inactivation. The combined results are interpreted to indicate that the locus of HOCl attack is the cell envelope, that HOCl inactivation does not occur by loss of membrane structural integrity, that loss of transport function can be identified with either selective oxidative inhibition of the transport proteins or loss of cellular metabolic energy, and that different mechanisms of inactivation may exist for HOCl and NH2Cl.
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PMID:Effects of the putative neutrophil-generated toxin, hypochlorous acid, on membrane permeability and transport systems of Escherichia coli. 301 36

Studies indicated that prior growth of Staphylococcus aureus 196E on glycerol or maltose led to cells with repressed ability to produce staphylococcal enterotoxin A (SEA). A PTS- mutant (196E-MA) lacking the phosphoenolpyruvate phosphotransferase system (PTS), derived from strain 196E, showed considerably less repression of SEA synthesis when cells were grown in glycerol or maltose. Since SEA synthesis is not repressed in the PTS- mutant, repression of toxin synthesis by glycerol, maltose or glucose in S. aureus 196E appears to be related to the presence of a functional PTS irrespective of whether the carbohydrate requires the PTS for cell entry. With lactose as an inducer, glucose, glycerol, maltose or 2-deoxyglucose repressed the synthesis of beta-galactosidase in S. aureus 196E. It is postulated that these compounds repress enzyme synthesis by an inducer exclusion mechanism involving phosphorylated sugar intermediates. However, inducer exclusion probably does not explain the mechanism of repression of SEA synthesis by carbohydrates.
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PMID:Enterotoxin A synthesis in Staphylococcus aureus: inhibition by glycerol and maltose. 311 55

A beta-glucosidase (EC 3.2.1.21) was purified to homogeneity from cell-free extracts of an extremely thermophilic anaerobic bacterium. The enzyme has an Mr of 43,000 as determined by molecular-exclusion chromatography, has a pI of 4.55 and shows optimum activity at pH 6.2. The enzyme is active against a wide range of aryl beta-glycosides and beta-linked disaccharides, with beta-galactosidase activity only slightly less than beta-glucosidase activity, and significant beta-xylosidase activity. Lineweaver-Burk plots for p-nitrophenyl beta-glucoside, o-nitrophenyl beta-glucoside and cellobiose substrates are biphasic concave-downwards. Inhibition of the beta-glucosidase by substrates and glucose is negligible. Thermal inactivation follows first-order kinetics, with t1/2 (65 degrees C) 45 h, t1/2 (75 degrees C) 47 min and t1/2 (85 degrees C) 1.4 min and a deactivation energy of 380 kJ/mol at pH 6.2. At pH 7.0, which is the optimum pH for thermostability, t1/2 (75 degrees C) is 130 min. At 75 degrees C, at pH 6.2, the thermostability is enhanced about 8-fold by 10% (w/v) glycerol, about 6-fold by 0.2 M-cellobiose and about 3-fold by 5 mM-dithiothreitol and 5 mM-2-mercaptoethanol.
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PMID:Purification and properties of a stable beta-glucosidase from an extremely thermophilic anaerobic bacterium. 311 33

The Escherichia coli glpT gene encodes a transport protein that mediates uptake of sn-glycerol-3-phosphate. This permease is a member of a class of bacterial organophosphate permeases which transport substrates by antiport with inorganic phosphate. The glpT gene product, probably an oligomer of a single polypeptide chain, is thought to span the cytoplasmic membrane several times, as predicted by the hydropathic profile. Protein fusions, in which varying lengths of the amino-terminal end of the permease is attached to alkaline phosphatase (phoA) and to beta-galactosidase (lacZ) were constructed. On the assumption that phoA fusions only exhibit high enzymatic activity when fused to extra-cytoplasmic regions of the target protein, whereas lacZ fusions will only be active when the beta-galactosidase portion is attached to cytoplasmic domains of the target protein, the activities of the fusions were used to test a two-dimensional model for the permease. The model proposes that GlpT contains 12 transmembrane segments divided by a larger cytoplasmic region. Despite some limitation caused by hot-spot sites of transpositions, the TnphoA approach was consistent with the model. In contrast, we feel that the enzymatic activity of lacZ fusions is only a limited parameter for studying the topology of a complex membrane protein.
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PMID:The transmembrane topology of the sn-glycerol-3-phosphate permease of Escherichia coli analysed by phoA and lacZ protein fusions. 314 44

The mitochondrial tricarboxylic acid cycle enzyme malate dehydrogenase was purified from Saccharomyces cerevisiae, and an antibody to the purified enzyme was obtained in rabbits. Immunoscreening of a yeast genomic DNA library cloned into a lambda gt11 expression vector with anti-malate dehydrogenase immunoglobulin G resulted in identification of a lambda recombinant encoding an immunoreactive beta-galactosidase fusion protein. The yeast DNA portion of the coding region for the fusion protein translates into an amino acid sequence which is very similar to carboxy-terminal sequences of malate dehydrogenases from other organisms. In s. cerevisiae transformed with a multicopy plasmid carrying the complete malate dehydrogenase gene, the specific activity and immunoreactivity of the mitochondrial isozyme are increased by eightfold. Expression of both the chromosomal and plasmid-borne genes is repressed by growth on glucose. Disruption of the chromosomal malate dehydrogenase gene in haploid S. cerevisiae produces mutants unable to grow on acetate and impaired in growth on glycerol plus lactate as carbon sources.
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PMID:Isolation and expression of the gene encoding yeast mitochondrial malate dehydrogenase. 331 68


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