Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 amino acid sequence in the 8 cyanogen bromide peptides comprising the central segment of beta-galactosidase is presented. This portion of the molecule, about 27% of the protein, contains over 40% of the lysine and tyrosine residues and has a slight excess of basic amino acids.
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PMID:Amino acid sequence of beta-galactosidase. IX. Sequence of the central segment, CNBr peptides 10 to 17, residues 378 to 653. 9 96

The sequence of the COOH-terminal third (omega) of beta-galactosidase is presented. The size of the 7 cyanogen bromide peptides of this segment is larger on the average, about 52 amino acid residues as compared to an average size of 42 for cyanogen bromide peptides in the whole molecule. Tyrosine, phenylalanine, and valine are low in this segment whereas alanine and lysine are high. This region has a slight excess of basic groups.
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PMID:Amino acid sequence of beta-galactosidase. X. Sequence of the COOH-terminal segment, CNBr peptides 18 to 24, residues 654 to 1021. 9 97

1. The location of the bivalent metal cation with respect to bound competitive inhibitors in Escherichia coli (lacZ) beta-galactosidase was investigated by proton magnetic resonance. 2. Replacement of Mg(2+) by Mn(2+) enhances both longitudinal and transverse relaxation of the methyl groups of the beta-d-galactopyranosyltrimethylammonium ion, and of methyl 1-thio-beta-d-galactopyranoside; linewidths are narrowed by increasing temperature. 3. The Mn(2+) ion is located 8-9A (0.8-0.9nm) from the centroid of the trimethylammonium group and 9A (0.9nm) from the average position of the methylthio protons. 4. The effective charge at the active site was probed by measurement of competitive inhibition constants (K(i) (o) and K(i) (+) respectively) for the isosteric ligands, beta-d-galactopyranosylbenzene and the beta-d-galactopyranosylpyridinium ion. 5. The ratio of inhibition constants (Q=K(i) (+)/K(i) (o)) obtained with 2-(beta-d-galactopyranosyl)-naphthalene and the beta-d-galactopyranosylisoquinolinium ion at pH7 with Mg(2+)-enzyme was identical, within experimental error, with that obtained with the monocyclic compounds. 6. The variation of Q for Mg(2+)-enzyme can be described by Q=0.1(1+[H(+)]/4.17x10(-10))/1+[H(+)]/10(-8)). 7. This, in the theoretical form for a single ionizable group, is ascribed to the ionization of the phenolic hydroxy group of tyrosine-501. 8. The variation of Q for Mg(2+)-free enzyme is complex, probably because of deprotonation of the groups normally attached to Mg(2+) as well as tyrosine-501.
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PMID:Interaction of the lacZ beta-galactosidase of Escherichia coli with some beta-D-galactopyranoside competitive inhibitors. 10 43

An endoproteolytic enzyme of Escherichia coli, designated protease III, has been purified about 9,600-fold to homogeneity with a 6% yield. The purified enzyme consists of a single polypeptide chain of Mr 110,000 and is most active at pH 7.4. Protease III is very sensitive to metal-chelating agents and reducing agents. The EDTA-inactivated enzyme can be reactivated by Zn2+, Co2+ or Mn2+. Protease III is devoid of activity toward aminopeptidase, carboxypeptidase, or esterase substrates but rapidly degrades small proteins. When fragments of beta-galactosidase are used as substrates for protease III, the enzyme preferentially degrades proteins with molecular weights of less than 7,000. Protease III cleaves the oxidized insulin B chain at two sites with an initial rapid cleavage at Tyr-Leu (16-17) and a second slower cut at Phe-Tyr (25-26).
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PMID:Purification and characterization of protease III from Escherichia coli. 37 13

The Escherichia coli lacZ ochre mutant strain U118 was converted to an amber mutant and suppressed with supF, which inserts tyrosine. Enzymatically active beta-galactosidase was isolated. It contained tyrosine at residue number 17 instead of glutamic acid as in wild type.
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PMID:Position of the mutation in beta-galactosidase ochre mutant U118. 41 41

Some preparations of beta-galactosidase from strains of Escherichia coli carrying point mutations in their lacZ genes did not precipitate with antibody as effectively as wild-type enzyme, but did not appear to be chain-terminating mutations as judged by polarity measurements and suppression. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude extracts of induced Lac+ strains revealed that the monomer of beta-galactosidase ran as a band uncontaminated by other cellular proteins. This method was used to identify missense mutations in the alpha and beta portions of the lacZ gene. Six of 13 mutations investigated were judged to be missense by this criterion. Measurement of the degree of polarity, the ability to complement a nonsense mutation at the operator-distal extremity of the gene (omega-complementation), and suppressibility by 12 nonsense suppressors allowed the assignment of six other mutations as either number or ochre. The protein figments produced by these six nonsense mutations appeared to be degraded in vivo. One mutation that could not be classified was either a missense mutation whose protein product was degraded or a very leak nonsense mutation. Two lacZ alleles were suppressed by the ochre suppressors supM and supN, although they were missense by other criteria. The ability of supM to suppress both nonsense and missense mutations can be explained if it is derived from a tyrosine transfer ribonucleic acid with a modified base in the first position of the anticodon. The mutations assigned to the missense class were not suppressed by the missense suppressors supH, supQ, glyV, glyU, or glyT. Our results suggest that the criteria used in the past to distinguish between nonsense and missense mutations may not be conclusive even when used together.
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PMID:Genetic and biochemical characterization of some missense mutations in the lacZ gene of Escherichia coli K-12. 78 Mar 38

Three members of the Src family of tyrosine kinases [pp60c-src (Src), p59fyn (Fyn) and pp62c-yes (Yes)] are ubiquitously expressed, and are thus likely to have general roles in growth control. We have previously shown that, after addition of platelet-derived growth factor (PDGF) to quiescent cells, all three kinases become activated and associated with the PDGF receptor. We have now addressed the requirements for this association. First, we have used a baculovirus expression system to show that Fyn associates with the activated PDGF receptor in vitro in the absence of other proteins, demonstrating that the association between the two molecules is direct. Second, by generating cell lines expressing chimeric molecules consisting of Fyn sequences fused to a portion of beta-galactosidase, we found that the SH2 domain of Fyn is necessary for ligand-stimulated association with the PDGF receptor in vivo. Third, those fusion proteins that associated with the PDGF receptor also became phosphorylated in vivo following PDGF treatment, and in in vitro kinase assays, suggesting that the amino-terminal half of Fyn contains the sites of PDGF-stimulated phosphorylation. Partially purified, kinase-negative Fyn also became phosphorylated in the activated PDGF receptor complex in vitro, demonstrating that the PDGF receptor phosphorylates Fyn, rather than the novel phosphorylations occurring by autophosphorylation.
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PMID:Association of Fyn with the activated platelet-derived growth factor receptor: requirements for binding and phosphorylation. 140 31

We have synthesized an antisense oligonucleotide primer that matches a supposedly conserved sequence in messages for heparan sulfate proteoglycans with transmembrane orientations. With the aid of this primer we have amplified partial and selected full-length copies of a message from human lung fibroblasts that codes for a novel integral membrane heparan sulfate proteoglycan. The encoded protein is 198 amino-acids long, with discrete cytoplasmic, transmembrane, and amino-terminal extracellular domains. Except for the sequences that represent putative heparan sulfate chain attachment sites, the extracellular domain of this protein has a unique structure. The transmembrane and cytoplasmic domains, in contrast, are highly similar to the corresponding domains of fibroglycan and syndecan, the two cell surface proteoglycans that figured as models for the design of the antisense primer. This similarity includes the conservation of four tyrosine residues, one immediately in front of the stop transfer sequence and three in the cytoplasmic segment, and of the most proximal and most distal cytoplasmic sequences. The cDNA detects a single 2.6-kb message in cultured human lung fibroblasts and in a variety of human epithelial and fibroblastic cell lines. Polyclonal and monoclonal antibodies raised against the encoded peptide after expression as a beta-galactosidase fusion protein react with the 35-kD coreprotein of a cell surface heparan sulfate proteoglycan of human lung fibroblasts and decorate the surface of many cell types. We propose to name this proteoglycan "amphiglycan" (from the Greek words amphi, "around, on both sides of" and amphoo, "both") referring to its domain structure which extends on both sides of the plasmamembrane, and to its localization around cells of both epithelial and fibroblastic origin.
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PMID:Molecular cloning of amphiglycan, a novel integral membrane heparan sulfate proteoglycan expressed by epithelial and fibroblastic cells. 150 Apr 33

Several neurological diseases which affect the corpus striatum are candidates for gene therapy. We have developed a defective Herpes Simplex Virus (HSV-1) vector system to introduce genes into postmitotic cells, such as neurons. The prototype vector, pHSVlac, contains a transcription unit which places the E. coli Lac Z gene under the control of the HSV-1 immediate early (IE) 4/5 promoter, a constitutive promoter. We now demonstrate that a HSV-1 vector can deliver a gene into striatal neurons. Infection of cultured rat striatal neurons with pHSVlac virus resulted in stable expression of beta-galactosidase for at least two weeks, without cell death. The potential to replace the Lac Z gene with other genes of interest, such as the gene responsible for Huntington's Disease, once it is isolated, may lead to insights about the pathogenesis of this genetic neurodegenerative disease, and may provide a method for performing gene therapy on this disease. Similarly, introduction of the tyrosine hydroxylase gene, which encodes the rate-limiting enzyme in the conversion of tyrosine to dopamine, into striatal neurons might provide a novel gene therapy approach towards treating Parkinson's Disease.
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PMID:Infection of cultured striatal neurons with a defective HSV-1 vector: implications for gene therapy. 166 13

A combination of gene transfer and intracerebral grafting may provide a powerful technique for examining the role of discrete substances in the development or functioning of the brain. In the present study, primary fibroblasts obtained from a skin biopsy from inbred Fischer rats were used as donor cells for genetic modification and grafting. When grafted to the striatum of Fischer rats with a prior 6-hydroxydopamine lesion, primary fibroblasts containing a transgene for either tyrosine hydroxylase (TH) or beta-galactosidase survived for 10 weeks and continued to express the transgene. TH synthesized by the implanted fibroblasts appeared to convert tyrosine to L-dopa actively, as observed in vitro, and to affect the host brain, as assessed through a behavioral measurement. These results suggest that primary fibroblasts genetically altered to express TH have the capacity to deliver L-dopa locally to the striatum in quantities sufficient to compensate partially for the loss of intrinsic striatal dopaminergic input.
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PMID:Survival and function of intrastriatally grafted primary fibroblasts genetically modified to produce L-dopa. 167 72


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