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 immune response to beta-galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23)is characterized by a wave of early help followed by a wave of suppression to a subsequent in vitro challenge with galactosidase-fluorescein. A cyanogen bromide peptide of beta-galactosidase, CB2, mimics the suppression seen with the enzyme. It is time dependent, carrier specific, and anti-theta sensitive; however, this suppression is not preceded by a wave of help. It is possible that CB2 cannot stimulate helpers, and is only able to activate suppressor cells. These data indicate that one small region of an antigen, capable of activating suppressors, can nullify the positive effect induced in helper T cells reactive with other epitopes on beta-galactosidase. Key determinants on macromolecules may in this way be influential in regulating the immune response to the entire antigen molecule.
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PMID:Key antigenic determinants in regulation of the immune response. 7 36

alpha Complementation in beta-galactosidase is the restoration of enzyme activity by addition of the alpha donor CNBr2, from amino acid residues 3--92 of the polypeptide, to inactive M15 protein from the lacZ deletion mutant strain M15. M15 protein lacks residues 11--41 and is a dimer; the active complex, like native beta-galactosidase, is tetrameric [Langley, K. E., & Zabin, I. (1976) Biochemistry 15, 4866--4875]. A dimer--dimer binding region in beta-galactosidase has been identified by proteolytic and immunologic studies of alpha-complementation. Proteolytic experiments were carried out with trypsin. Treatment of native beta-galactosidase with trypsin, followed by reaction of the mixture with cyanogen bromide, yields intact CNBr2 as measured by its ability to complement M15 protein. Active CNBr2 is not obtained when urea-denatured beta-galactosidase is treated in the same way. Therefore the segment corresponding to CNBr2 is apparently buried within the folded protein. Immunologic experiments were carried out with antibodies against CNBr2, tryptic peptide T8 (residues 60--140), and CNBr3 (residues 93--187). Anti-CNBr2 and anti-T8 bind to M15 protein but not to beta-galactosidase, indicating that this area is exposed in the dimer. Anti CNBr2, but not anti-T8 or anti-CNBr3, inhibits the formation of alpha-complemented enzyme. These results indicate that an early part of the sequence, within the segment corresponding to CNBr2, is involved in dimer--dimer interaction.
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PMID:A dimer--dimer binding region in beta-galactosidase. 8 82

All of the 24 cyanogen bromide peptides of beta-galactosidase have been isolated in pure form. Of these 8 ranged in size from 2 to 5 residues and were purified by paper electrophoresis. The 16 large peptides, from 23 to 119 residues, were chromatographed at pH 5.0 on a carboxymethyl-cellulose column in 0.02 M ammonium acetate buffer containing 8 M urea. A number of peptides were obtained in pure from following Sephadex G-50 or G-75 gel filtration. Others were separated on sulfopropyl-Sephadex or diethyl-(2-hydroxylpropylaminoethyl)-Sephadex. There large peptides were obtained in over 50% yield and several others were obtained in more than 25% yield.
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PMID:Amino acid sequence of beta-galactosidase. VII. Isolation of the 24 cyanogen bromide peptides. 9 94

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

The amino acid sequence of beta-galactosidase has been determined. The monomer contains 1,021 amino acid residues in a single polypeptide chain and has a molecular weight of 116,349. All 80 tryptic peptides as well as all 24 CNBr peptides have been isolated in pure form. Evidence is presented for the ordering of the CNBr peptides. The sequence determination was aided by analysis of cyanogen bromide peptides obtained from a polypeptide fragment produced by a lacZ termination mutant strain.
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PMID:Amino acid sequence of beta-galactosidase. XI. Peptide ordering procedures and the complete sequence. 9 98

Antibodies were prepared against 18 tryptic and cyanogen bromide peptides from beta-galactosidase ranging in size from 15 to 96 amino acid residues representing more than 80% of the polypeptide chain. They were tested for binding capacity and affinity toward their homologous antigens and toward the whole native protein. Nine antisera bound to beta-galactosidase; these had been raised against certain peptides from the central and carboxyl-terminal regions of the poly-peptide chain. Based on these results a preliminary model of the three-dimensional structure of the folded protein is suggested.
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PMID:Probes of beta-galactosidase structure with antibodies. Reaction of anti-peptide antibodies against native enzyme. 10 69

A protein possessing both lac repressor and beta-galactosidase activities in a single polypeptide of about 155,000 daltons was purified from a deletion mutant of Escherichia coli in which the lacI and Z genes are fused. A 77-residue cyanogen bromide peptide containing the fusion joint was isolated. A radioimmunoassay with an antibody prepared against CNBr2 (residues 3-92) of beta-galactosidase was used to monitor its purification. The sequence of the joining peptide was determined by analysis of tryptic peptides and by automatic sequencer analysis. The site of joining is from residue 355 of lac repressor to residue 24 of beta-galactosidase (or 356 to 25), indicating that the last 4 residues at the carboxyl terminus of lac repressor and the first 23 residues at the amino terminus of beta-galactosidase are not essential for the activities of these two proteins. The exact site of the fusion is not known because lac repressor residue 356 and beta-galactosidase residue 24 are both leucine residues. Examination of the nucleotide sequences around the two end points of the deletion revealed a homology of 9 identities in a stretch of 11 base pairs.
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PMID:beta-Galactosidase chimeras: primary structure of a lac repressor-beta-galactosidase protein. 10 58

We have purified beta-galactosidase and beta-glucuronidase from macrophages of thioglycollate-treated mice using concanavalin A chromatography and immunoprecipitation. The apparent molecular weight of the beta-galactosidase subunit, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, changed during a long term pulse-chase experiment. Following a 1-h pulse with [3H]leucine, radiolabel was present exclusively in an Mr = 82,000 form. However, after a 3-h chase in medium containing unlabeled leucine, most label migrated at Mr = 63,000, and at 24 h, all label was in the Mr = 63,000 form. Electrophoresis of peptides produced by cyanogen bromide cleavage of immunoprecipitates demonstrated structural similarities between precursor and mature forms. A mutation in the mouse, which is known to depress the rate of synthesis of beta-galactosidase in many cell types, proportionately decreased incorporation of [3H]leucine into both the Mr = 82,000 and 63,000 forms. Therefore, by kinetic, structural, and genetic evidence, the large molecular weight beta-galactosidase is a precursor of mature macrophage enzyme. No precursor of the Mr = 75,000 subunit of beta-glucuronidase was detected.
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PMID:Biosynthesis of two lysosomal enzymes in macrophages. Evidence for a precursor of beta-galactosidase. 11 27

A gene for somatostatin, a mammalian peptide (14 amino acid residues) hormone, was synthesized by chemical methods. This gene was fused to the Escherichia coli beta-galactosidase gene on the plasmid pBR322. Transformation of E. coli with the chimeric plasmid DNA led to the synthesis of a polypeptide including the sequence of amino acids corresponding to somatostatin. In vitro, active somatostatin was specifically cleaved from the large chimeric protein by treatment with cyanogen bromide. This represents the first synthesis of a functional polypeptide product from a gene of chemically synthesized origin.
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PMID:Expression in Escherichia coli of a chemically synthesized gene for the hormone somatostatin. 41 51


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