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)

The ilvBNC operon of Corynebacterium glutamicum encodes acetohydroxy acid synthase and isomero-reductase, which are key enzymes of L-isoleucine, L-valine and L-leucine syntheses. In this study we identified the transcript initiation site of ilvBNC operon 292 nucleotides in front of the first structural gene, and detected the formation of a short transcript from the leader region in addition to the full-length transcript of the operon. This identifies the control of ilvBNC transcription by an attenuation mechanism involving antitermination. Mutations in the leader region were made and their effect on the operon expression in ilvB'lacZ fusions was quantified. Although a presumed leader-peptide-coding region is only one nucleotide away from the transcript initiation site determined, there is clear evidence to support the formation of this leader peptide: (i) the substitution of initiation codon ATG of the peptide by AGG reduced lacZ expression of the appropriate fusion construct to 19%; (ii) the replacement of three subsequent Val codons by Ala codons resulted in the loss of Val-dependent expression; and (iii) a leader peptide LacZ fusion resulted in active beta-galactosidase. Based on these results, it is concluded that transcription of ilvBNC is controlled by a translational-coupled attenuation mechanism. The absence of a ribosome binding site for leader peptide formation means that additional mechanisms may contribute to the transcription control at the decoding initiation step in the leader peptide formation.
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PMID:Attenuation control of ilvBNC in Corynebacterium glutamicum: evidence of leader peptide formation without the presence of a ribosome binding site. 1623 99

A 365-base-pair (bp) DNA fragment, containing the promoter region of the nitrogenase reductase (nifH) gene from stem Rhizobium BTAi1, has been isolated and sequenced. The transcription initiation sites were localized at positions 152 (major initiation) and 114 (minor initiation) nucleotides upstream of the translation initiation codon. The 200-bp nucleotide sequence upstream of the nifH structural gene shows substantial homology to the corresponding nifH regions of cowpea Rhizobium (100%), Parasponia Rhizobium (89%), and Rhizobium japonicum (88%). The nifH promoter region of stem Rhizobium BTAi1 was fused to the lacZ gene of Escherichia coli. The fusion and a 1.6-kilobase DNA specifying neomycin phosphotransferase were inserted into a 3,4-kilobase fragment of stem Rhizobium chromosome, and the resulting construct was placed on a mobilizable vector, pREV1000. Stem Rhizobium transconjugants resistant to kanamycin were found to contain the nifH promoter region-lacZ fusion linked to the neomycin phosphotransferase gene at the site of chromosomal homology. Analysis of the DNA from stable transconjugants showed integration of a single copy of these sequences into the chromosome by a double-reciprocal crossover event. The transconjugants formed nitrogen-fixing nodules, indicating that the insertion occurred in a "nonessential" region of the stem Rhizobium chromosome. Transconjugant strain BTAi1000 grows on beta-galactosidase indicator plates under aerobic conditions as white colonies, whereas under microaerobic conditions (97% N(2)/3% O(2)), which derepress nitrogenase, the colonies turn blue within 15-24 hr. beta-Galactosidase activity in derepressed cultures of BTAi1000 showed a 200-fold increase in comparison to the wild-type strain, whereas stem nodules formed by BTAi1000 exhibited 15- to 20-fold higher beta-galactosidase values than wild-type nodules. Nitrogenase promoter-dependent expression of beta-galactosidase in stem nodules was inhibited by fixed nitrogen, suggesting that the nifH promoter-lacZ fusion is controlled coordinately in trans with the native nif region.
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PMID:Expression of beta-galactosidase controlled by a nitrogenase promoter in stem nodules of Aeschynomene scabra. 1659 14

The ability of Hypocrea jecorina (Trichoderma reesei) to grow on lactose strongly depends on the formation of an extracellular glycoside hydrolase (GH) family 35 beta-galactosidase, encoded by the bga1 gene. Previous studies, using batch or transfer cultures of pregrown cells, had shown that bga1 is induced by lactose and d-galactose, but to a lesser extent by galactitol. To test whether the induction level is influenced by the different growth rates attainable on these carbon sources, bga1 expression was compared in carbon-limited chemostat cultivations at defined dilution (=specific growth) rates. The data showed that bga1 expression by lactose, d-galactose and galactitol positively correlated with the dilution rate, and that galactitol and d-galactose induced the highest activities of beta-galactosidase at comparable growth rates. To know more about the actual inducer for beta-galactosidase formation, its expression in H. jecorina strains impaired in the first steps of the two d-galactose-degrading pathways was compared. Induction by d-galactose and galactitol was still found in strains deleted in the galactokinase-encoding gene gal1, which is responsible for the first step of the Leloir pathway of d-galactose catabolism. However, in a strain deleted in the aldose/d-xylose reductase gene xyl1, which performs the reduction of d-galactose to galactitol in a recently identified second pathway, induction by d-galactose, but not by galactitol, was impaired. On the other hand, induction by d-galactose and galactitol was not affected in an l-arabinitol 4-dehydrogenase (lad1)-deleted strain which is impaired in the subsequent step of galactitol degradation. These results indicate that galactitol is the actual inducer of Bga1 formation during growth on d-galactose in H. jecorina.
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PMID:Induction of extracellular beta-galactosidase (Bga1) formation by D-galactose in Hypocrea jecorina is mediated by galactitol. 1725 22

This study reports the vital regulatory influence of Xyr1 (xylanase regulator 1) on the transcription of hydrolytic enzyme-encoding genes and hydrolase formation on lactose in Hypocrea jecorina. While the transcription of the xyr1 gene itself is achieved by release of carbon catabolite repression, the transcript formation of xyn1 (xylanase 1) is regulated by an additional induction mechanism mediated by lactose. Xyr1 has an important impact on lactose metabolism by directly activating xyl1 (xylose reductase 1) transcription and indirectly influencing transcription of bga1 (beta-galactosidase 1). The latter is achieved by regulating the conversion of D-galactose to the inducing carbon source galactitol.
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PMID:Xyr1 receives the lactose induction signal and regulates lactose metabolism in Hypocrea jecorina. 1766 82

The Hypocrea jecorina D-xylose reductase encoding gene xyl1 shows low basal transcript levels, and is induced by D-xylose, L-arabinose and L-arabinitol and, to a lesser extent, by lactose, D-galactose, galactitol and xylitol. The recombinantly expressed XYL1 catalyzes the NADPH-dependent reduction of the pentoses D-xylose and L-arabinose and the hexose D-galactose. Deletion of xyl1 slightly reduces growth on all carbon sources, but a significant decrease is found on D-xylose, L-arabinose and D-galactose. Similar to pentose degradation, XYL1 reduces D-galactose to galactitol in a recently identified second D-galactose pathway. Strains impaired in both D-galactose pathways are almost unable to grow on D-galactose. Deltaxyl1 strains show reduced growth on lactose and are impaired in beta-galactosidase expression and induction of the major cellobiohydrolase gene cbh1. A strain deleted in the cellulase regulator XYR1 is even more severely impaired in growth and beta-galactosidase expression on lactose, and does not produce any cbh1 transcript at all. In this strain, only a low basal level of xyl1 transcription is found on lactose. Galactitol, but not D-galactose is able to induce xyl1 transcription in a XYR1-independent manner. Our results show that the role of the H. jecorina XYL1 is not restricted to D-xylose catabolism and demonstrates its importance for induction of cellulases and beta-galactosidases.
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PMID:The D-xylose reductase of Hypocrea jecorina is the major aldose reductase in pentose and D-galactose catabolism and necessary for beta-galactosidase and cellulase induction by lactose. 1792 46

Microarray analysis revealed that the expression of ferric reductase (FRP1) can be regulated by the Riml01 protein. In order to find new transcriptional regulatory element in the promoter of FRP1, we analyzed the 1000 bp sequence upstream of ATG to find 2 potential Riml01p binding sites. We generated site-specific mutations in each of the two sites and fused these mutated promoters to LacZ. Then the promoter-LacZ fusion construct was recombinant into wild type and riml01-/- strains for beta-galactosidase assay. The results revealed that the FRP1 was up-regulated in alkaline pH and this was caused by iron starvation. The -650 site, not the -160 site, had an important role in FRP1 Riml01p-dependent expression. We conclude that Riml01p may interact with the -650 binding site of the promoter to regulate the FRP1 expression.
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PMID:[Regulating promoter element of iron-dependent gene FRP1 in Candida albicans by site-directed mutation]. 1899 34

The opportunistic pathogen Candida albicans develops different systems to acquire essential nutrients such as iron. The Rim101 pathway controls gene expression to adapt to different environments through transcription factor Rim101p. Ferric reductase genes are important for iron acquisition, but further work should be carried out to show about how ferric reductase genes are regulated. In this study we demonstrate that ferric reductase FRP1 expression is upregulated by alkaline pH and iron-limited conditions. Moreover, promoter deletion identified that the upregulated elements lie in -822 to 437 and 263 to -124 and the downregulated elements in -437 to -263 using a beta-galactosidase reporter system. Using electrophoretic mobility shift assay we also found that Rim101p can bind directly with two putative 5'-CCAAGAA-3' sites at the -157 and -629 sites. Interestingly, site-specific mutations show that only the -629 site, not the -157 site, plays an important role in FRP1 expression under iron-limited conditions.
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PMID:Candida albicans ferric reductase FRP1 is regulated by direct interaction with Rim101p transcription factor. 1907 41


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