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

A new gene expression system in mammalian cells was developed by using the glucocorticoid receptor (GR) as an inducible positive feedback factor. Mouse Ltk- cells were transfected with plasmids carrying the GR-encoding gene and the lacZ reporter gene, both of which were fused with the glucocorticoid-inducible enhancer/promotor of the mouse mammary tumor virus (MTV). The GR gene was first induced to supply the receptor protein, which further induced the expression of both GR and reporter genes. Stable transformants induced with dexamethasone, a synthetic glucocorticoid hormone, demonstrated beta-galactosidase activity 60-140-fold higher than uninduced controls. Similarly, the human alpha-interferon-encoding gene fused with the MTV enhancer/promoter was induced more than 12,000-fold. This system allowed us to increase the expression of the reporter or target genes without augmenting basal levels of expression significantly, and may be useful to investigate the unknown function of a cloned gene, particularly when the gene product of interest is cytotoxic or growth-inhibiting.
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PMID:An auto-inducible vector conferring high glucocorticoid inducibility upon stable transformant cells. 255 71

Several relevant characteristics have been studied in nine Lactobacillus plantarum strains isolated from Cabrales cheese. They fermented lactose efficiently and possessed both beta-galactosidase and beta-phosphogalactosidase activities, but no significant proteolytic activity was detected. Antimicrobial susceptibility tests revealed no high level resistance to any of the fourteen compounds tested. All the strains had a high content of extrachromosomal DNA of unknown function. A recombinant plasmid comprising pUC19 from Escherichia coli and a small cryptic plasmid from L. plantarum has been constructed and may be used to develop a shuttle vector for these species.
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PMID:Selected characteristics of several strains of Lactobacillus plantarum. 262 83

We isolated and characterized cis-acting mutations that affect the regulation of the metB gene of Salmonella typhimurium LT2. The mutations were isolated in an Escherichia coli lac deletion strain lysogenized with lambda bacteriophage carrying a metB-lacZ gene fusion (lambda JBlac) in which beta-galactosidase production is dependent upon metB gene expression. The mutant lysogens show elevated, poorly regulated beta-galactosidase production. The altered regulation is a result of disruption of the methionine control system mediated by the metJ repressor. The mutations are located in a region of dyad symmetry centered near the -35 sequence of the metB promoter. We propose that these mutations alter the repressor binding site and define the metB operator sequence. In addition, we discuss a highly conserved, nonsymmetric DNA sequence of unknown function which occurs in the control regions of the metA, metC, metE, metF, metG, and metJB genes of both S. typhimurium and E. coli.
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PMID:Mutations affecting the regulation of the metB gene of Salmonella typhimurium LT2. 294 97

A 9500-bp DNA segment containing the adenylate cyclase gene (cya) of Escherichia coli has been isolated and analyzed. Four large proteins are encoded within this fragment - the adenylate cyclase protein (92 kDal), two proteins of unknown function (37 and 32 kDal), and a part of the uvrD-coded protein. Various truncated adenylate cyclase proteins, made from cya genes having as much as 60% of their carboxy-terminal end deleted, are sufficient to complement cya- hosts. When these truncated cya genes are present on a multicopy plasmid in a cya- host, the synthesis of beta-galactosidase is still regulated by glucose. The "maxicell" technique was used to visualize the four proteins encoded by this region and some of the truncated adenylate cyclase proteins.
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PMID:Analysis of the cya locus of Escherichia coli. 632 17

The HSP90 gene of the yeast Saccharomyces cerevisiae encodes a heat shock-inducible protein with an Mr of 90,000 (hsp90) and unknown function. We fused DNA fragments of a known sequence (namely, either end of a 1.4-kilobase EcoRI fragment which contains the S. cerevisiae TRP1 gene) to an EcoRI site within the coding sequence of the HSP90 gene. When these fusions are introduced into S. cerevisiae they direct the synthesis of unique truncated hsp90 proteins. By determining the size and charge of these proteins we were able to deduce the translational reading frame at the (EcoRI) fusion site. This information allowed us to design and construct a well-defined in-frame fusion between the S. cerevisiae HSP90 gene and the Escherichia coli lacZ gene. When this fused gene is introduced into S. cerevisiae on a multicopy plasmid vector, it directs the heat shock-inducible synthesis of a fused protein, which is an enzymatically active beta-galactosidase. Thus, for the first time, it is possible to quantitate the heat shock response in a eucaryotic organism with a simple enzyme assay.
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PMID:Heat shock-regulated production of Escherichia coli beta-galactosidase in Saccharomyces cerevisiae. 641 4

Changes in expression of ribosomal protein genes during growth and stationary phase of Streptomyces coelicolor A3(2) in liquid medium were studied. Proteins being synthesized were pulse-labelled with [35S]-methionine, separated by two-dimensional polyacrylamide gel electrophoresis, and quantified using the BioImage computer software. Most of the ribosomal proteins were synthesized throughout the life cycle. Exceptions were two proteins whose synthesis drastically decreased at the approach of stationary phase. These two proteins were identified in purified ribosomes as homologues of Escherichia coli ribosomal proteins L10 and L7/L12, using antibodies raised against fusion proteins between these ribosomal proteins and Escherichia coli beta-galactosidase. The genes (rplJ and rplL) encoding the L10 and L7/L12 proteins were contained in a 1.2 kb BamHI fragment that was cloned and sequenced. The linkage and order of the genes coincide with other L10-L7/L12 operons. However, L11 and L1 genes were not present immediately upstream of the L10 gene, as is the case for E. coli and other bacteria. Instead, two open reading frames of unknown function were found immediately upstream of the L10 gene, in an adjacent 1.9 kb BamHI fragment.
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PMID:Synthesis of ribosomal proteins during growth of Streptomyces coelicolor. 754 48

A sensitive two-site enzyme immunoassay (EIA) system was established for human pS2 protein, a small estrogen-inducible secretory protein of unknown function originally identified in MCF-7 human breast cancer cells. Our EIA system is based on the sandwiching of antigen between anti-recombinant (r) pS2 antibody IgG coated on a polystyrene plate and biotinylated anti-rpS2 antibody IgG. The amount of pS2 protein was quantified by measurement of the bound enzyme activity of subsequently added streptavidin-linked beta-D-galactosidase (beta-D-galactosidase, EC 3.2.1.23). pS2 protein purified from MCF-7 culture supernatants was detectable at a concentration as low as 3 pg/ml (corresponding to 60 fg/well). This EIA system revealed that the amount of pS2-like immunoreactivity (LI) in human urine was 13.6 ng/mg creatinine (median, n = 416) and that there was no correlation between the pS2-LI concentration in urine and sex or aging. pS2-LI levels in plasma and sera of the normal subjects were 392 pg/ml (median, n = 14) and 494 pg/ml (median, n = 12), respectively. The serum level of the patients with breast cancer (528 pg/ml; median, n = 67) was not statistically different from that of normal subjects, although high levels of pS2 protein in breast cancer tissues had been reported.
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PMID:Estimation of pS2 protein level in human body fluids by a sensitive two-site enzyme immunoassay. 798 37

We identified several linked genes of a lactose regulon in Rhizobium meliloti. These were lacZ, the structural gene for beta-galactosidase; lacR, the lactose repressor gene; and two genes encoding proteins of unknown function, lacW and lacX. Insertion mutants in lacW and lacZ belonged to a single genetic complementation group, and lacW appeared to lie upstream of lacZ in an operon. Expression of lacZ, lacW and lacX was repressed by lacR, and expression of lacZ and lacW was derepressed by lactose. lacZ was not required for induction of lacW by lactose, suggesting that lactose itself, rather than a processed form of lactose, may be the actual inducer molecule. Expression of all three genes was repressed by succinate, and the lacR independence of this repression showed that inducer exclusion could not be the sole mechanism. This pattern of lac gene organization and regulation differs in several ways from that observed in enteric bacteria.
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PMID:Genetic characterization of a Rhizobium meliloti lactose utilization locus. 814 40

The 8th step in the 10-step heme biosynthetic pathway of Salmonella typhimurium is the oxidation of coproporphyrinogen III to protoporphyrinogen IX. On the basis of genetic studies, we have suggested that this reaction may be catalyzed by either of two different enzymes, an oxygen-dependent one encoded by hemF or an oxygen-independent enzyme encoded by hemN. Here, we report the cloning of the S. typhimurium hemF gene and its DNA sequence. The predicted amino acid sequence of the HemF protein is 44% identical to that of the coproporphyrinogen oxidase encoded by the yeast HEM13 gene. The wild-type S. typhimurium strain LT-2 produces an oxygen-dependent coproporphyrinogen oxidase activity detectable in crude extracts, which is not found in hemF mutants and is overproduced in strains carrying the hemF gene on a multicopy plasmid. the hemF gene is the second gene in an operon with an upstream gene with an unknown function, whose amino acid sequence suggests a relation to amidases involved in cell wall synthesis or remodeling. The upstream gene and hemF are cotranscribed from a promoter which was mapped by primer extension. A weaker, hemF-specific promoter is inferred from the behavior of an omega-Cm insertion mutation in the upstream gene. Although this insertion decreases expression of beta-galactosidase about 7.5-fold when placed upstream of a hemF-lacZ operon fusion, it still allows sufficient HemF expression from an otherwise wild-type construct to confer a Hem+ phenotype. The hemF operon is transcribed clockwise with respect to the genetic map.
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PMID:An oxygen-dependent coproporphyrinogen oxidase encoded by the hemF gene of Salmonella typhimurium. 834 42


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