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 promoter of the threonine operon was joined to the structural genes of the lac operon in Escherichia coli K 12. The synthesis of beta-galactosidase was thus repressed by threonine plus isoleucine in the fusion strains. To isolate mutations which affect the expression of the threonine operon, alterations in the level of expression of the lacZ gene were selected. A new type of regulatory mutation was discovered.
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PMID:New regulatory mutations affecting the expression of the threonine operon in Escherichia coli K-12. 9 15

We have isolated strains of Escherichia coli in which an amino-terminal portion of the cytoplasmic enzyme beta-galactosidase is replaced by an amino-terminal portion of the periplasmic enzyme alkaline phosphatase. The synthesis of these hybrid proteins is regulated by inorganic phosphate and they are located in the cytoplasm. One of these proteins was purified, and 14 amino acids of the amino-terminal sequence were determined. The first five amino acids, Met-Lys-Gln-Ser-Thr, appear to represent a portion of the signal sequence of the precursor of alkaline phosphatase, and the remaining sequence corresponds to that of beta-galactosidase, beginning at amino acid residue 20. The approach described here could be used for the analysis of signal sequences of exported proteins and for partial amino acid sequence determination of certain of certain other proteins.
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PMID:Use of gene fusions to determine a partial signal sequence of alkaline phosphatase. 11 91

The amino acid sequence of beta-galactosidase was determined. The protein contains 1021 amino acid residues in a single polypeptide chain. The subunit molecular weight calculated from the sequence is 116,248. The sequence determination, carried out mainly by conventional methods, was aided by complementation tests, by the use of termination mutant strains, and by a new immunochemical method. The five residue sequence Thr-Pro-His-Pro-Ala appears twice within the polypeptide chain, but no other striking homologous features are evident.
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PMID:The amino acid sequence of beta-galactosidase of Escherichia coli. 32 55

Intracistronic alpha-complementation between a cyanogen bromide digest of beta-galactosidase and an extract of the lac Zminus operator-proximal deletion mutant M15 was used to monitor the purification of a cyanogen bromide peptide (CB2) responsible for the complementation. Key steps in the purification were ion exchange chromatography on carboxymethylcellulose and sulfopropyl-Sephadex in the presence of urea, and Sephadex gel filtration. CB2 contains residues 3 to 92 of beta-galactosidase. Its sequence is: Ile-Thr-Asp-Ser-Leu-Ala-Val-Val-Leu-Gln-Arg-Arg-Asp-Trp-Glu-Asn-Pro-Gly-Val-Thr-Gln-Leu-Asn-Arg-Leu-Ala-Ala-His-Pro-Pro-Phe-Ala-Ser-Trp-Arg-Asn-Ser-Glu-Glu-Ala-Arg-Thr-Asp-Arg-Pro-Ser-Gln-Gln-Leu-Arg-Ser-Leu-Asn-Gly-Glu-Trp-Arg-Phe-Ala-Trp-Phe-Pro-Ala-Pro-Glu-Ala-Val-Pro-Glu-Ser-Trp-Leu-Glu-Cys-Asp-Leu-Pro-Glu-Ala-Asp-Thr-Val-Val-Val-Pro-Ser-Asn-Trp-Gln-Met. Thus no more than 1/13 of the beta-galactosidase polypeptide chain, starting 2 residues from the NH2 terminus, is necessary for alpha-complementation with M15 as alpha-acceptor.
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PMID:Amino acid sequence of beta-galactosidase. IV. Sequence of an alpha-complementing cyanogen bromide peptide, residues 3 to 92. 109 37

Clinical findings were compared with the results of molecular analysis in 16 Japanese patients from 10 unrelated families with the adult/chronic form of GM1 gangliosidosis. Age of onset ranged from 3 to 30 years. Major clinical manifestations were gait and speech disturbances caused by persistent muscle hypertonia. Dystonic postures and movements, facial grimacing, and parkinsonian manifestations were commonly seen. Cerebellar signs, myoclonus, severe intellectual impairment, dysmorphism, or visceromegaly were not observed. A common single-base substitution, 51Ile(ATC)----Thr(ACC), reported in a previous study of ours, was confirmed in 14 patients by the Bsu36I restriction site analysis; one was a compound heterozygote with another mutation (457Arg[CGA]----Gln[CAA]) and the others were homozygotes of this mutation. Clinically, the compound-heterozygous patient showed more severe neurological manifestations and a more rapid clinical course than those of homozygotes. The homozygotes showed considerable variations in the age of onset and subsequent clinical course. The 51Ile----Thr mutant allele expressed a significant amount of beta-galactosidase activity, whereas the 457Arg----Gln mutant allele expressed extremely low activity in human GM1 gangliosidosis fibroblasts. We conclude that these gene mutations causing different residual enzyme activities are related to the severity of clinical manifestations, but some other genetic or environmental factors contribute to clinical heterogeneity. The Bsu36I restriction site analysis was performed in 7 families and provided clear results for the diagnosis of heterozygotes as well as homozygotes of this specific clinical form of GM1 gangliosidosis. The technique is applicable to prenatal diagnosis and genetic counseling.
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PMID:GM1 gangliosidosis in adults: clinical and molecular analysis of 16 Japanese patients. 135 43

The DF3 antigen is a member of a family of high molecular weight glycoproteins aberrantly expressed in malignant mammary epithelium. We have generated a monoclonal antibody (MAb), designated DF3-P, against a recombinant DF3/beta-galactosidase fusion protein. Characterization of this MAb has demonstrated reactivity with immature precursors of DF3 antigen and not with the secreted form. These findings are in contrast to those obtained with MAb DF3, a previously described antibody with predominant reactivity against the mature glycoprotein. The finding that deglycosylation of secreted DF3 antigen with neuraminidase and endo-alpha-N-acetylgalactosaminidase is associated with increased MAb DF3-P reactivity provided additional support for the selectivity of this antibody against the protein core. Epitope mapping studies demonstrate that both the DF3-P and DF3 epitopes are located at a TRPAPGS domain in the 20-amino acid tandem repeat. The results of competition studies with synthetic peptides indicate that the proline in this domain is involved in both epitopes, while the potential glycosylation sites at threonine and serine may contribute to the differential reactivity of MAbs DF3 and DF3-P. Taken together, these findings suggest that both antibodies react with a similar epitope that is modified by the presence of carbohydrate moieties. The results of immunoperoxidase staining studies further demonstrate that while MAb DF3-P reacts with formalin-fixed sections of breast carcinomas, this antibody exhibits little if any reactivity with normal mammary epithelium. Selective expression of the DF3-P epitope in malignant breast cells may be useful in identifying this transformed phenotype.
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PMID:Tumor selective reactivity of a monoclonal antibody prepared against a recombinant peptide derived from the DF3 human breast carcinoma-associated antigen. 137 71

The effect of 8-oxo-2'-deoxyguanosine (8-oxo-dG) (8-hydroxydeoxyguanosine)--a DNA base damage product induced by oxygen radicals and irradiation on survival and mutagenesis in Escherichia coli strains C-600 and P-687 was investigated. Survival and mutagenesis curves, in dependence of 8-oxo-dG concentrations in the medium, ranging from 0.2 through 10 mM, were obtained. Bacterial survival at all 8-oxo-dG concentrations tested was shown to be no lesser than in the control. The mutagenic effect of 8-oxo-dG was tested by frequency of reversions in the absence of leucine and threonine. A non-linear dependence of mutagenesis on the concentration was observed. Linear increase in the amount of revertants took place at concentrations of 8-oxo-dG lower than 1 mM, and being kept constant at higher concentrations. Induction of SOS repair under the action of 8-oxo-dG in E. coli PQ37 strain was estimated according to alteration of activity of beta-galactosidase in the SOS chromotest. Weak induction of the SOS response was observed within the wide range of 8-oxo-dG concentration values, which points to a lack of genotoxicity and independence of mutagenesis on SOS repair.
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PMID:[Mutagenic effect on Escherichia coli bacteria of 8-hydroxy-2'-deoxyguanosine--a DNA base damage product induced by oxygen radicals and ionizing radiation]. 142 57

The XylS protein is the positive regulator of the TOL plasmid-encoded meta-cleavage pathway for the metabolism of alkylbenzoates in Pseudomonas putida. This protein is activated by a variety of benzoate analogues. To elucidate the functional domains of the regulator and their interactions, several fusions of the XylS C-terminus to MS2 polymerase and of the N-terminus to beta-galactosidase were constructed but all are inactive. In addition, 15 double mutant xylS genes were constructed in vitro by fusing parts of various mutant genes to produce mutant regulators exhibiting C-terminal and N-terminal amino acid substitutions. The phenotypic properties of the parental single mutant genes, and those of the double mutant genes, suggest that the C-terminal region is involved in binding to DNA sequences at the promoter of the meta-cleavage pathway operon, and that the benzoate effector binding pocket includes critical residues present at both the N-terminal and C-terminal ends of the protein. The intraallelic dominance of the Ile229 (Ser229-->Ile) and Val274 (Asp274-->Val) substitutions over the N-terminal His41 (Arg41-->His) substitution, and the intraallelic dominance of Thr45 (Arg45-->Thr) over Ile229 and Val274, support the proposal that these two regions of the regulator interact functionally. Combination of the Leu88 (Trp88-->Leu) and Arg256 (Pro256-->Arg) substitutions did not suppress the semiconstitutive phenotype conferred by Leu88, but resulted in a protein with altered ability to recognize benzoates. In contrast, the Leu88 semiconstitutive phenotype was suppressed by Val288 (Asp288-->Val), and the double mutant was susceptible to activation by benzoates.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:XylS domain interactions can be deduced from intraallelic dominance in double mutants of Pseudomonas putida. 146 13

A 14-bp segment in the promoter region of the tdcABC operon of Escherichia coli shows sequence identity with the consensus binding site for the E. coli integration host factor (IHF). In an himA (IHF-deficient) strain, expression of beta-galactosidase from a tdcB'-'lacZ protein fusion plasmid was about 10% of that seen with an isogenic himA+ strain. Threonine dehydratase activity from the chromosomal tdcB gene in the himA mutant was also about 10% of the wild-type enzyme level. Two different mutations introduced into the putative IHF-binding site in the fusion plasmid greatly reduced the plasmid-coded beta-galactosidase activity in cells containing IHF. In vitro gel retardation and DNase I footprinting analyses showed binding of purified IHF to the wild-type but not to the mutant promoter. IHF protected a 31-bp region between -118 and -88 encompassing the conserved IHF consensus sequence. These results suggest that efficient expression of the tdc operon in vivo requires a functional IHF and an IHF-binding site in the tdc promoter.
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PMID:Integration host factor is required for positive regulation of the tdc operon of Escherichia coli. 172 11

An active preparation of human phospholipase A2 (PLA2) was made after expression as an insoluble fusion protein in Escherichia coli. The new key elements required for PLA2 isolation were the maintenance of the fusion protein in solution after the initial solubilization and the use of a tryptophan cleavage procedure for regeneration of native PLA2 from the fusion protein. The fusion protein was composed of a beta-galactosidase leader peptide incorporating six consecutive threonine residues to aid in insoluble inclusion body formation, followed by a tryptophan adjacent to the N-terminus of PLA2. The fusion protein was purified from cell lysates, and the leader peptide was cleaved on the C-terminal side of the tryptophan residue with N-chlorosuccinimide. The released PLA2 was refolded and renatured to produce an enzyme with activity comparable to that of other phospholipases A2.
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PMID:A strategy for obtaining active mammalian enzyme from a fusion protein expressed in bacteria using phospholipase A2 as a model. 182 81


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