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)

Several E. coli mutants were isolated which produce triple chimeras between one of the trp enzymes lac, repressor and beta-galactosidase. The mutants were isolated as TonB- Lac+ derivatives of a phenotypically Lac- TrpR- strain carrying a lac I+ -Z+ fusion on a phi80dlac phage. The phage is integrated into the chromosome in such a way that the lac and the trp genes are transcribed in the same direction. Of a total of 58 candidates 2 TrpA- and 3 Trp- strains produce triple chimeras. The chimeras from the two TrpA- strians were further examined. They consist of tryptophan synthetase alpha-subunit, lac repressor and beta-galactosidase. In crude extracts of these strains the tryptophan synthetase alpha-subunit part can be identified by its ability to aggregate with the beta-subunit since some of the beta-subunit activity can be precipitated with antiserum against beta-galactosidase. Furthermore beta-galactosidase precipitates with antiserum against tryptophan synthetase alpha-subunit. The lac repressor part is able to bind IPTG, but not lac operator DNA in vitro. The beta-galactosidase part is as unaffected as in the original lac repressor-beta-galactosidase chimera. The molecular weights of both chimeras are 175,000 when determined by SDS gel electrophoresis. The chimeras are partially degraded giving rise to fragments of distinct molecular weights.
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PMID:Synthetic multifunctional proteins: isolation of covalently linked tryptophan synthetase alpha-subunit-lac-repressor-beta-galactosidase chimeras. 41 64

Colicinogenic factors ColI and ColV, which have been shown to behave as sex factors, could not be induced with mitomycin C. In contrast, the ColE(1), ColE(2), and ColE(3) factors, which do not exhibit any fertility factor characteristics, are inducible by this agent. The induced production of colicins E(1), E(2), and E(3) was accompanied by a loss in viability at a concentration of mitomycin C which was bacteriostatic to noncolicinogenic cells or to cells carrying the ColV or ColI factors. The loss in viability accompanying the mitomycin C induction of the ColE(1), ColE(2), or ColE(3) factors also occurred when colicin synthesis was blocked by chloramphenicol or amino acid starvation. However, chloramphenicol was able to block the loss of viability of a recipient cell after mitomycin C induction of a newly acquired Col factor if the antibiotic was present throughout the mating period. No detectable internal colicin or colicin precursor could be demonstrated during the lag period prior to the appearance of colicin outside the cell 20 to 30 min after the addition of mitomycin C. If chloramphenicol was present during the lag period following the addition of mitomycin C, colicin synthesis began immediately after the removal of these antibiotics. The synthesis of tryptophan synthetase and induced beta-galactosidase proceeded normally throughout the lag period and well into the period of colicin production. Regulation of beta-galactosidase synthesis did not seem to be profoundly affected during the lag period subsequent to mitomycin C addition. Induced colicin synthesis, like bacterial or induced prophage protein synthesis, was subject to inhibition by virulent phage infection.
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PMID:Comparative study of the events associated with colicin induction. 534 Jun 80

Seven hybridoma clones, producing antibodies directed against the beta 2-subunit of Escherichia coli tryptophan synthase, have been obtained from mouse cells. To test whether the corresponding monoclonal antibodies recognize different epitopes on beta 2, an ELISA double antibody binding system has been developed and is reported here. The antigen is first coated onto a microtitration plate. Two monoclonal antibodies are then added either separately or simultaneously, and the amount of bound antibody is quantitatively measured by use of immunoglobulin (rabbit anti-mouse IgG) linked to beta-galactosidase. Additivity of the bound enzymatic activity is observed when the monoclonal antibodies bind to distinct epitopes. Using this test, it is shown that, of the 7 anti-beta 2 monoclonal antibodies obtained, 5 recognize the same antigenic site and the 2 others recognize a second site.
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PMID:A convenient enzyme-linked immunosorbent assay for testing whether monoclonal antibodies recognize the same antigenic site. Application to hybridomas specific for the beta 2-subunit of Escherichia coli tryptophan synthase. 618 14