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)

Previous studies described lacZ'- and cat'-'cpxA fusion genes whose expression restored to normal all the phenotypic defects associated with cpxA mutations (Albin, R., and Silverman, P. M. (1984) Mol. Gen. Genet. 197, 272-279). Here, we show by DNA nucleotide sequence analysis that the fusion genes encode 241 carboxyl-terminal amino acids of the CpxA polypeptide. Using this information, we constructed a fusion gene containing the same 241 cpxA codons preceded by 1007 codons of beta-galactosidase. The resultant hybrid polypeptide was purified and used to raise an anti-(CpxA polypeptide) antiserum. Using the antiserum, we have identified the chromsomal Escherichia coli K12 cpxA gene product as a 52-kDa polypeptide. The polypeptide showed temperature-sensitive accumulation in a strain carrying both the cpxA2[Ts] and cpxB1 alleles and accumulated to a level higher than normal in cells that carried a high-copy number, cpxA+ plasmid. Immune precipitates of in vitro transcription-translation reactions with cpxA+ plasmids as template also contained a 52-kDa polypeptide, indistinguishable in electrophoretic mobility from the immunoreactive polypeptide synthesized in vivo. Two regions of amino acid sequence at the carboxyl-terminus of the CpxA polypeptide are significantly homologous to corresponding regions of the E. coli K12 EnvZ polypeptide, an inner membrane component that, like the CpxA polypeptide, is required to maintain the protein composition of the cell envelope. The cpxA coding sequence is followed by two repetitive extragenic palindrome sequences in opposite orientation.
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PMID:The Cpx proteins of Escherichia coli K12. Immunologic detection of the chromosomal cpxA gene product. 300 73

The subcellular location of LamB-LacZ hybrid proteins in the Escherichia coli K12 strains pop3234 and pop3299 was investigated by immunocytochemical detection and protease-accessibility experiments. Induction of the synthesis of the hybrid proteins resulted in the appearance of membrane-like structures within the cytoplasm of the cells. Labelling of ultrathin cryosections of the cells with anti-beta-galactosidase or anti-LamB protein serum and protein-A-gold complexes revealed that the hybrid proteins were associated with these membrane-like structures or accumulated within the cytoplasm. Protease-accessibility experiments confirmed this localization. Moreover, when low quantities of hybrid proteins were produced, i.e. in uninduced pop3234 cells or in induced pop3299 cells, the hybrid proteins were accessible to trypsin from the periplasmic side of the inner membrane, leaving protected fragments with an apparent Mr of 83,000. Apparently, these hybrid proteins are partly translocated through the inner membrane, resulting in membrane-spanning forms of the proteins.
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PMID:Accumulation of LamB-LacZ hybrid proteins in intracytoplasmic membrane-like structures in Escherichia coli K12. 305 74

The "SOS Chromotest" has recently been introduced by P. Quillardet et al. (1982; Quillardet and Hofnung, 1985), who use strain PQ37 of Escherichia coli K12 to test for genotoxicity. We have modified the procedure in order to optimize the determination of beta-galactosidase and alkaline phosphatase activities, and, where possible, to allow measurements to be made automatically. Kinetic determination is quicker, more sensitive and avoids interference by coloured compounds. Modification of the metabolic activation system increases the sensitivity of the test for progenotoxicity.
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PMID:Kinetic determination of enzymatic activity and modification of the metabolic activation system in the SOS chromotest. 309 30

The SOS-function-inducing activities of 36 furylethylenes were characterized in Escherichia coli K12. The induction of the SOS function was assayed by monitoring the beta-galactosidase activity in the sulA::lacZ fusion strain PQ 37. To correct for the inhibitory effects of test compounds on mRNA or protein synthesis, the level of the constitutive alkaline phosphatase was assayed in parallel. Tested furylethylenes included nine alkylesters and eleven N-alkylamides of 5-nitro-2-furylacrylic acid (NFAA) and fourteen derivatives differing not only in substituents at exocyclic double bond, but also in the position 5 of the furan ring. The induction of the SOS-function by the derivatives depends on the presence of 5-nitrofuran centre in their molecule; side chains in the position 2 modify the degree of SOS response. SOS-inducing potency of n-alkyl congeners decreases with increasing lipophilicity. Effect of derivatives with branched alkyl substituents is lower than expected from the behavior of the n-alkyl homologues. All derivatives with positive effect on SOS-function in E. coli show mutagenic activity on Salmonella typhimurium TA98 in Ames test.
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PMID:Relationships between structure of 5-nitro-2-furylethylenes and their SOS-function-inducing activities in Escherichia coli. 351 69

A study was made of the SOS induction of the gene sulA of Escherichia coli K12 in relation to the gene dosage of the gene recA. In experiments the sulA::lacZ fusion strain PQ37 and derivatives of PQ37 with the multi-copy plasmids pDR1453 or pBR322 were used. The SOS response was induced with nitrofurantoin, SOS induction of the gene sulA was determined on the basis of the amount of beta-galactosidase synthesized, i.e. by the SOS chromotest (Quillardet et al., 1982a). It was found in this work that cells with the plasmid pDR1453, which contain the gene recA of E. coli K12 (Sancar and Rupp, 1979), have a decreased SOS induction of the gene sulA. Cells with the plasmid pBR322 do not exhibit this decrease. Inactivation of the gene recA in the plasmid pDR1453 with preservation of the functional gene recA in the chromosome leads to a restoration of 'standard' SOS induction of the gene sulA. The results show that the amount of the gene product of the gene recA affects the SOS induction of the gene sulA.
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PMID:SOS induction of the gene sulA is partly inhibited in Escherichia coli K12 cells overproducing the RecA protein. 352 42

We have identified mutations in three different chromosomal genes of Escherichia coli K12 which reduce sensitivity to microcin B17. Mutations in ompF and ompR genes affected production of an outer membrane porin protein, OmpF, and resulted in reduced sensitivity to a number of other agents (colicins, bacteriophages) besides microcin B17. The third class of mutants were specifically and highly resistant to microcin B17. The mutations in these strains were mapped to a gene (sbmA), located at 8.7 min on the E. coli K12 chromosome, which is closely linked to phoA. The wild-type sbmA allele was cloned into multiple copy number plasmids, and its location within the cloned DNA fragment was further defined by mutagenesis with MiniMudII1681. These insertion mutations resulted in in-frame fusions between the sbmA and lacZ genes, thereby allowing us to determine the direction of sbmA gene transcription. Plasmids carrying these gene fusions produced low levels of beta-galactosidase, indicating that the sbmA gene is poorly expressed. We have been unable to identify the sbmA gene product, but indirect evidence indicates that it might be an envelope protein involved in microcin uptake.
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PMID:Identification, mapping, cloning and characterization of a gene (sbmA) required for microcin B17 action on Escherichia coli K12. 354 11

Sixty-three strains of E. coli transconjugants derived from E. coli K12 J62-1 containing plasmids derived from Klebsiella pneumoniae, were examined for the presence of phenotypic markers other than antibiotic resistance. This investigation was carried out using API 50CHE and API ZYM tests. Beta-glucosidase was found in 63/63 J62-1 transconjugants. Dulcitol dehydrogenase was present in 92.1% while beta-galactosidase was present in 70% of transconjugants. None of the three enzymes were present in the recipient. Dulcitol dehydrogenase was present only in the transconjugants and is absent from the donors and recipient. The transconjugants, cured of their antibiotic resistant plasmids retained dulcitol dehydrogenase activity. The Klebsiella donors were not cured of antibiotic resistance by the curing process.
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PMID:Biochemical characterization of E. coli transconjugants with plasmids derived from Klebsiella pneumoniae. 389 56

We have sequenced the ebgA (evolved beta-galactosidase) gene of Escherichia coli K12. The sequence shows 50% nucleotide identity with the E. coli lacZ gene, demonstrating that the two genes are related by descent from a common ancestral gene. Comparison of the two sequences suggests that the ebgA gene has recently been under selection. A significant excess of identical, rather than synonymous, codons used to encode identical amino acids at the same positions in the aligned sequences implies that some form of selection is operating directly at the DNA level. This selection is independent of, and in addition to, selection based on codon usage or on function of the gene products.
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PMID:Sequence of the ebgA gene of Escherichia coli: comparison with the lacZ gene. 393 7

Mutants of E. coli K12 with deletions of the beta-galactosidase gene (lacZ) can reacquire the ability to hydrolyze beta-galactosides during prolonged intense selection for growth on lactose. Full lactose competence is restored through a sequence of at least five mutations. Cell extracts of these derived strains hydrolyze o-nitrophenyl-beta-D-galactoside, the standard substrate for assay of beta-galactosidase. The enzyme responsible for this activity differs in its immunological, kinetic, and sedimentation characteristics from the lacZ beta-galactosidase of wild-type E. coli. Its genetic determinant, designated ebg-5, maps at 59 min on the E. coli chromosome, whereas the lac operon maps at 10 min. We suggest that a gene not involved in lactose utilization has been progressively changed into a form capable of specifying a beta-galactosidase and that this process is similar to that whereby genes with new functions are evolved by natural selection.
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PMID:Evolution of a second gene for beta-galactosidase in Escherichia coli. 412 6

1. Experiments were devised to show whether catabolite repression of beta-galactosidase synthesis operates at the level of transcription or of translation. Escherichia coli K12 was induced for a short period in non-repressing medium (glycerol-minimal medium), and transcription of the lac operon was terminated by either of two methods; glucose was then added as a source of the catabolite repressor during the subsequent translation of the accumulated beta-galactosidase messenger RNA. 2. When induced bacteria in glycerol medium were infected with T6 phage, which is known to halt transcription, the addition of glucose up to 3min. later diminished the yield of beta-galactosidase. 3. When induced bacteria in glycerol medium were removed from the inducer and resuspended in fresh medium (a process that is also known to halt transcription), the yield of enzyme was again diminished by the presence of glucose in the resuspension medium. 4. It is concluded that repression of beta-galactosidase synthesis can be brought about by the presence of glucose during the translation phase only. 5. In E. coli strain 300U the effect on translation was sufficient to account for almost all the catabolite repression of beta-galactosidase synthesis observed during exponential growth of the organism in glucose-minimal medium. In E. coli strain 200P, however, much more severe repression occurred during exponential growth, and an additional effect of glucose is postulated.
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PMID:Carabolite repression of the lac operon. Repression of translation. 489 2


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