Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proteus mirabilis, a common agent of nosocomially acquired and catheter-associated urinary tract infection, is the most frequent cause of infection-induced bladder and kidney stones. Urease-catalyzed urea hydrolysis initiates stone formation in urine and can be inhibited by acetohydroxamic acid and other structural analogs of urea. Since P. mirabilis urease is inducible with urea, there has been some concern that urease inhibitors actually induce urease during an active infection, thus compounding the problem of elevated enzyme activity. Quantitating induction by compounds that simultaneously inhibit urease activity has been difficult. Therefore, to study these problems, we constructed a fusion of ureA (a urease subunit gene) and lacZ (the beta-galactosidase gene) within plasmid pMID1010, which encodes an inducible urease of P. mirabilis expressed in E. coli JM103 (Lac-). The fusion protein, predicted to be 117 kDa, was induced by urea and detected on Western blots (immunoblots) with anti-beta-galactosidase antiserum. Peak beta-galactosidase activity of 9.9 mumol of ONPG (o-nitrophenyl-beta-D-galactopyranoside) hydrolyzed per min per mg of protein, quantitated spectrophotometrically, was induced at 200 mM urea. The uninduced rate was 0.2 mumol of ONPG hydrolyzed per min per mg of protein. Induction was specific for urea, as no structural analog of urea (including acetohydroxamic acid, hydroxyurea, thiourea, hippuric acid, flurofamide, or hydroxylamine) induced fusion protein activity. These data suggest that induction by inactivation of UreR, the urease repressor protein that governs regulation of the urease operon, is specific for urea and does not respond to closely related structural analogs.
 ...
PMID:Proteus mirabilis urease: use of a ureA-lacZ fusion demonstrates that induction is highly specific for urea. 189 50

In this study we further define cell surface carbohydrate structures relevant to cellular interactions that regulate erythropoiesis. An analysis of thymocyte cell surface negativity was made using fluoresceinated poly-L-ornithine (FITC poly-L-ornithine) as a probe that binds to negatively charged sites (i.e., sialic acid residues) at the cell surface. Two distinct subpopulations are labeled, comprising both intensely as well as weakly fluorescent subpopulations of thymocytes. Prior treatment of thymocytes with Vibrio cholerae neuraminidase (VCN), which removes cell surface sialic acid residues, markedly reduced the FITC poly-L-ornithine surface labeling of these cells. Distinct enzymatic modifications of regulatory cell functions were also assessed by the ability of thymocytes to function as separate regulatory subpopulations. Confirming our previous observations, treating thymocytes with VCN impaired the enhancement activity but had little effect on thymocyte regulatory ability to suppress erythroid colony growth. In contrast, treatment of thymocytes with galactose oxidase (GAO) or beta-galactosidase (beta-GAL) removed suppressor activity either before or after VCN treatment. A further exposure of GAO-treated thymocytes to sodium borohydride or hydroxylamine, which reduce D-galactose residues, restores their suppressor function and prevents enhancement. These differential enzymatic effects on thymocyte regulatory cell functions suggest that different carbohydrate structures may be involved in helper and suppressor activities for erythroid colony formation. Sialic acid residues may be associated with certain cells that function to enhance erythropoiesis, and D-galactose residues may be associated with the suppressor subpopulation.
 ...
PMID:Effects of neuraminidase on the regulation of erythropoiesis: III: Characterization of carbohydrate moieties on the surface of thymic regulatory cells that interact with erythroid colony-forming cells. 256 44

Salmonella typhimurium produces H2S from thiosulfate or sulfite. The respective pathways for the two reductions must be distinct as mutants carrying motations in phs, chlA, and menB reduced sulfite, but not thiosulfate, to H2S, and glucose repressed the production of H2S from thiosulfate while it stimulated its production from sulfite. The phs and chlA mutants also lacked a methyl viologen-linked thiosulfate reductase activity present in anaerobically grown wild-type cultures. A number of hydroxylamine, transposon Tn10 insertion, and Mu d1(Apr lac) operon fusion mutants defective in phs were characterized. One of the hydroxylamine mutants was an amber mutant, as indicated by suppression of its mutation in a supD background. The temperature-sensitive phs mutants produced H2S and methyl viologen-linked thiosulfate reductase at 30 degrees C but not at 42 degrees C. The reductases in all such mutants grown at 30 degrees C were as thermostable as the wild-type enzyme and did not differ in electrophoretic relative mobility, suggesting that phs is not the structural gene for thiosulfate reductase. Expression of beta-galactosidase in phs::Mu d1(Apr lac) mutants was dependent on anaerobiosis and the presence of reduced sulfur. It was also strongly influenced by carbon source and growth stage. The results are consistent with a model in which the phs gene encodes a regulatory protein essential for the reduction of thiosulfate to hydrogen sulfide.
 ...
PMID:The phs gene and hydrogen sulfide production by Salmonella typhimurium. 310 33

The gene pheV from Escherichia coli, coding for tRNAPhe and carried on a plasmid, has been mutagenised with hydroxylamine. Mutants in the structural gene have been identified using two criteria: (i) de-attenuation of beta-galactosidase expression, while under the control of the attenuator region of the pheS,T operon by means of an operon fusion; (ii) loss of ability to complement thermosensitivity of a mutant Phe-tRNA synthetase. Mutants showing de-attenuation were sequenced and two nucleotide changes identified: G44----A44 (found five times) and m7G46----A46 (found once). Sequencing of mutants that lost complementation identified two further tRNA mutants, C2---U2 and G15----A15; the mutant m7G46----A46 was also re-isolated by this criterion. Three of the mutants involve bases implicated in tertiary rather than secondary structure hydrogen bonding. One hypothesis for the mechanism of de-attenuation is that mutant tRNAPhe molecules compete with the wild-type tRNAPhe on the ribosome but are inefficient at some step in the elongation process.
 ...
PMID:Functional mutants of phenylalanine transfer RNA from Escherichia coli. 389 9

Properties of the ribosome-bound beta-galactosidase were examined in Escherichia coli cells after prolonged induction. This fraction of enzyme was not chased from ribosomes by removal of inducer, or by treatments with hydroxylamine, puromycin, chloramphenicol, and azide. However, the metabolic turnover of this fraction could be demonstrated by means of a pulsed exposure to the phenylalanine analogue beta-2-thienylalanine, and this fraction was enriched in heavy forms relative to the soluble enzyme. These observations indicated a tight coupling of the release of ribosome-bound enzyme to nascent enzyme synthesis, and it is suggested that the ribosome-bound enzyme is related to an intermediate stage in the assembly of quarternary enzyme structures.
 ...
PMID:Nature of ribosome-bound beta-galactosidase. 554 27

The lac I gene of Escherichia coli encodes the lactose repressor. We isolated temperature-sensitive mutants of the lac I gene by in vitro mutagenesis with hydroxylamine. The new mutation sites were determined, and replacement of a single amino acid had respectively occurred at amino acid positions 241 (Ala-->Thr), 265 (Gly-->Asp) and 300 (Ser-->Asn). These mutation sites were located in the core region of the lac repressor protein. Temperature-dependent expression of beta-galactosidase was observed in the strains having these mutant lac I genes. By using these temperature-sensitive lac I genes, we developed a thermo-inducible expression system for a foreign gene under the control of the lac promoter. A recombinant fusion protein, consisting of a derivative of E. coli beta-galactosidase and the human calcitonin precursor peptide, was efficiently produced by using this system.
 ...
PMID:Thermo-inducible expression of a recombinant fusion protein by Escherichia coli lac repressor mutants. 776 12

The cDNA encoding sea bass (Dicentrarchus labrax) prolactin (sbPRL) was obtained by reverse transcription-polymerase chain reaction (RT/PCR) from pituitary RNA with degenerate primers designed on the basis of the cDNAs of the two PRLs (tPRL188 and tPRL177) from the tilapia, Oreochromis niloticus. The sbPRL cDNA encodes a preprotein of 212 amino acids composed of a putative signal peptide of 24 residues and a mature protein of 188 amino acids that is the homologue of tiPRL188. The cDNA coding for the mature protein was cloned into the pAX4a+ expression vector and expressed efficiently in Escherichia coli as a beta-galactosidase-fusion protein. To split the fusion protein, a sequence encoding the hexapeptide, (Asn-Gly)3, that contains three Asn-Gly hydroxylamine-cleavable bonds, had been previously introduced by PCR upstream of the sbPRL cDNA. N-terminal sequencing confirmed that the cleaved product corresponded to sbPRL. An antiserum raised against the recombinant hormone detected by immunoblotting a single band in sea bass pituitaries and two bands in tilapia pituitaries, suggesting the occurrence of a single PRL form in sea bass.
 ...
PMID:The prolactin of European sea bass (Dicentrarchus labrax L.): cloning of cDNA and efficient expression in Escherichia coli. 780 37

The closely related multidrug efflux pumps QacA and QacB, from the bacterial pathogen Staphylococcus aureus, both confer resistance to various toxic organic cations but differ in that QacB mediates lower levels of resistance to divalent cations. Cloning and nucleotide sequencing of the qacB gene revealed that qacB differs from qacA by only seven nucleotide substitutions. Random hydroxylamine mutagenesis of qacB was undertaken, selecting for variants that conferred increased resistance to divalent cations. Both QacA and the QacB mutants capable of conferring resistance to divalent cations contain an acidic residue at either amino acid 322 or 323, whereas QacB contains uncharged residues in these positions. Site-directed mutagenesis of qacA confirmed the importance of an acidic residue within this region of QacA in conferring resistance to divalent cations. Membrane topological analysis using alkaline phosphatase and beta-galactosidase fusions indicated that the QacA protein contains 14 transmembrane segments. Thus, QacA represents the first membrane transport protein shown to contain 14 transmembrane segments, and confirms that the major facilitator superfamily contains a family of proteins with 14 transmembrane segments.
 ...
PMID:Multidrug resistance proteins QacA and QacB from Staphylococcus aureus: membrane topology and identification of residues involved in substrate specificity. 862 87

Human insulin-like growth factor I (IGF-I) was expressed in Escherichia coli as a truncated beta-galactosidase-IGF-I fusion protein. The Lac Z" gene was truncated by removal of a 490 bp fragment which encoded 163 N-terminal residues of beta-galactosidase and was connected to the IGF-I cDNA by a linker encoding hydroxylamine cleavage recognition sequence. By truncating Lac Z" gene, the overall yield and purification procedures of IGF-I from fusion protein have been improved. The fusion protein was produced in the form of insoluble inclusion bodies with isopropyl-1-thio-beta-D-galactoside (IPTG) induction. After cleavage of the fusion protein with hydroxylamine, the released IGF-I was purified to homogeneity by a cation exchange chromatography, refolding and reverse-phase high performance liquid chromatography (rp-HPLC). The purified IGF-I was found to be indistinguishable from the native IGF-I by N-terminal amino acid sequence, SDS-polyacrylamide gel electrophoresis, and rp-HPLC and by biological activities such as thymidine uptake, protein synthesis and receptor binding. These results suggest that the expression and simple purification of recombinant human IGF-I described in this paper may be useful for large scale production of IGF-I.
 ...
PMID:High-level expression and simple purification of recombinant human insulin-like growth factor I. 881 76

The cDNA encoding promelittin was obtained from the total RNA of bee poison gland by RT-PCR. Moreover, hydroxylamine clearage site was arranged before the melittin sequences by site-directed mutagenesis. The expression vector containing the mutagenic promelittin sequence with partial sequence of beta-galactosidase was constructed. The result of DNA sequence analysis demonstrated that the obtained cDNA sequence include the desired codon and the reading frame of fusion gene was correct. The induced protein was expressed in Escherichia coli.
 ...
PMID:[Site-directed mutagenesis of melittin gene and its expression in Escherichia coli]. 1088 87


1 2 Next >>