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)

Because there are not yet direct assays for most of the proteins required for differentiation of Rhodobacter capsulatus cytoplasmic membrane into photosynthetically competent intracytoplasmic membrane, a molecular inquiry into the mechanism and regulation of this process is difficult. We have, therefore, chosen to isolate R. capsulatus photosynthesis genes by creating in-frame fusions to lac'Z vectors, and selecting for those that direct appropriately regulated levels of beta-galactosidase in R. capsulatus. One lacZ fusion isolate was used to identify an open reading frame (ORF) of unknown function and flanking sequences that promoted initiation of transcription. The chromosomal copy of this ORF was mutated by insertion of a kanamycin-resistant cartridge into the cloned fragment and substitution for the chromosomal copy by homologous recombination. The phenotype of the resultant mutant cells showed that the ORF encodes 2-desacetyl-2-hydroxyethyl bacteriochlorophyllide a dehydrogenase, an enzyme that catalyzes the penultimate step in bacteriochlorophyll a biosynthesis. The nucleotide sequence of this bchC gene and its 5' regulatory region were determined. The deduced amino acid sequence shows that the bchC gene encodes a 33-kDa protein that is less hydrophobic than integral membrane proteins of R. capsulatus, although there are hydrophobic segments that could in principle interact with a lipid membrane. Results of S1 nuclease protection and primer extension experiments show that a 5' mRNA end is positioned within the cloned segment, and that this 5' end maps to sequences with significant sequence similarity to the previously characterized puf operon promoter region.
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PMID:Promoter mapping and nucleotide sequence of the bchC bacteriochlorophyll biosynthesis gene from Rhodobacter capsulatus. 255 68

The Drosophila abnormal wing discs (awd) gene encodes the subunit of a protein that has nucleoside diphosphate kinase (NDP kinase) activity. Null mutations of the awd gene cause lethality after puparium formation. Larvae homozygous for such mutations have small imaginal discs, lymph glands, and brain lobes. Neither the imaginal discs nor the ovaries from such null mutant larvae are capable of further growth or normal differentiation when transplanted into suitable host larvae. This null mutant phenotype can be entirely rescued by one copy of a transgene that has 750 bp of awd upstream regulatory DNA fused to a full-length awd cDNA. Tissue-specific expression of AWD protein from this rescue transgene is identical to tissue-specific expression of beta-galactosidase from a reporter transgene that has the same regulatory region fused to the bacterial lac Z gene. However, this rescue transgene or reporter transgene expression pattern is only a subset of the endogenous pattern of expression detected by either in situ hybridization or immunohistochemistry. This suggests that awd is normally expressed in some tissues where it is not required. The null mutant phenotype cannot be rescued at all by a transgene that has 750 bp of awd upstream regulatory DNA fused to a full-length awd cDNA with a mutation that eliminates NDP kinase activity by replacement of the active site histidine with alanine. This suggests that the enzymatic activity of the AWD protein is necessary for its biological function. The human genes nm23-H1 and nm23-H2 encode NDP kinase A and B subunits, respectively. The protein subunit encoded by either human nm23 gene is 78% identical to that encoded by the Drosophila awd gene. Transgenes that have the 750-bp awd upstream regulatory DNA fused to human nm23-H2 cDNA but not to nm23-H1 cDNA can rescue the imaginal disc phenotype and the zygotic lethality caused by homozygosis for an awd null mutation as efficiently as an awd transgene. However, rescue of female sterility requires twice as much nm23-H2 expression as awd expression. This implies that the enzymatic activity of the AWD protein is not sufficient for its biological function. The biological function may require nonconserved residues of the AWD protein that allow it to interact with other proteins.
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PMID:The enzymatic activity of Drosophila AWD/NDP kinase is necessary but not sufficient for its biological function. 880 30

The Drosophila abnormal wing discs (awd) gene encodes the subunit of a protein that has nucleoside diphosphate kinase (NDP kinase) activity. Null mutations of the awd gene cause lethality after puparium formation. Larvae homozygous for such mutations have small imaginal discs, lymph glands, and brain lobes. Neither the imaginal discs nor the ovaries from such null mutant larvae are capable of further growth or normal differentiation when transplanted into suitable host larvae. This null mutant phenotype can be entirely rescued by one copy of a transgene that has 750 bp of awd upstream regulatory DNA fused to a full-length awd cDNA. Tissue-specific expression of AWD protein from this rescue transgene is identical to tissue-specific expression of beta-galactosidase from a reporter transgene that has the same regulatory region fused to the bacterial lac Z gene. However, this rescue transgene or reporter transgene expression pattern is only a subset of the endogenous pattern of expression detected by either in situ hybridization or immunohistochemistry. This suggests that awd is normally expressed in some tissues where it is not required. The null mutant phenotype cannot be rescued at all by a transgene that has 750 bp of awd upstream regulatory DNA fused to a full-length awd cDNA with a mutation that eliminates NDP kinase activity by replacement of the active site histidine with alanine. This suggests that the enzymatic activity of the AWD protein is necessary for its biological function. The human genes nm23-H1 and nm23-H2 encode NDP kinase A and B subunits, respectively. The protein subunit encoded by either human nm23 gene is 78% identical to that encoded by the Drosophila awd gene. Transgenes that have the 750-bp awd upstream regulatory DNA fused to human nm23-H2 cDNA but not to nm23-H1 cDNA can rescue the imaginal disc phenotype and the zygotic lethality caused by homozygosis for an awd null mutation as efficiently as an awd transgene. However, rescue of female sterility requires twice as much nm23-H2 expression as awd expression. This implies that the enzymatic activity of the AWD protein is not sufficient for its biological function. The biological function may require nonconserved residues of the AWD protein that allow it to interact with other proteins.
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PMID:The Enzymatic Activity of Drosophila AWD/NDP Kinase Is Necessary but Not Sufficient for Its Biological Function 881 47

Open reading frame orf192, which is located immediately upstream of the aerobic repressor gene crtJ, was genetically and biochemically demonstrated to code for a second aerobic repressor (AerR) of photosynthesis gene expression in Rhodobacter capsulatus. Promoter-mapping studies indicate that crtJ has its own promoter but that a significant proportion of crtJ expression is promoted by read-through transcription of orf192 (aerR) transcripts through crtJ. Disruption of aerR resulted in increased photopigment biosynthesis during aerobic growth to a level similar to that of disruption of crtJ. Like that reported for CrtJ, beta-galactosidase assays of reporter gene expression indicated that disruption of aerR resulted in a two- to threefold increase in aerobic expression of the crtI and pucB operons. However, unlike CrtJ, AerR aerobically represses puf operon expression and does not aerobically repress bchC expression. Gel mobility shift analysis with purified AerR indicates that AerR does not bind to a bchC promoter probe but does bind to the crtI, puc, and puf promoter probes. These results indicate that AerR is a DNA-binding protein that targets genes partially overlapping a subset of genes that are also controlled by CrtJ. We also provide evidence for cooperative binding of AerR and CrtJ to the puc promoter region.
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PMID:AerR, a second aerobic repressor of photosynthesis gene expression in Rhodobacter capsulatus. 1197 10

Citrus unshiu is freeze tolerant to -10 degrees C when fully acclimated after exposure to cold, nonfreezing temperatures. To gain an understanding of its cold tolerance mechanism, mRNA differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) and quantitative relative RT-PCR were used to study gene expression under a gradual cold-acclimation temperature regime. Six up-regulated and two down regulated genes were identified based on their amino acid sequences. The identified proteins encoded by the up-regulated genes were: 14-3-3 protein, 40S ribosomal protein S23, putative 60S ribosomal protein L15, nucleoside diphosphate kinase III protein, regulator of chromosome condensation-like protein, and amino acid permease 6. The proteins encoded by the two down-regulated genes were: miraculin-like protein and beta-galactosidase. Their individual function has been briefly reviewed based on published information. In addition to the findings in this study, we compared the function of cold responsive genes of Poncirus trifoliata, a very cold hardy relative of Citrus species that is freeze tolerant to -30 degrees C when fully acclimated, to the function of genes in the current study.
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PMID:Identification of cold acclimated genes in leaves of Citrus unshiu by mRNA differential display. 1612 77