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)

A recently identified, high m.w. human tumor antigen, reactive with monoclonal antibody (MAb) PD41 and designated prostate mucin antigen (PMA), was found to have expression highly restricted to prostate carcinomas. Both biochemical and immunological characteristics of this antigen and its relationship to other tumor-associated mucins and various species of submaxillary mucins were evaluated. Immunohistochemical examination of submaxillary tissues revealed differential expression of this antigen and other human tumor-associated mucins, with MAb PD41 expression found only in bovine submaxillary gland serous cells. Neuraminidase treatment enhanced antibody binding by 50%, suggesting partial masking of the PD41 epitope by sialic acid. Antigenicity was reduced by treatment with alkaline-borohydride, sodium metaperiodate, beta-galactosidase, O-glycanase, and various proteolytic enzymes. MAb PD41 antibody binding also could be significantly reduced by selected lectins and sugars suggesting that the immunodominant carbohydrate involved in the epitope was an O-linked oligosaccharide containing N-acetyl galactosamine as a major component. This antigen was further distinguished from T, Tn, or Sialyl-Tn antigens and blood group carbohydrate antigens by radioimmunometric analyses. Cross-blocking and double determinant RIA experiments also showed a distinction between the PD41 epitope and several well-characterized tumor-associated mucin antigens such as MUCI, CEA, M344, OCI25, and AR3 as well as bovine submaxillary core protein. Our results indicate that the PD41-reactive epitope is a non-acidic O-linked carbohydrate or glycopeptide epitope with restricted expression in prostate carcinomas and bovine submaxillary glands. This expression is distinct from other mucin-like tumor-associated antigens identified in human prostate carcinomas.
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PMID:Characterization of a prostate carcinoma mucin-like antigen (PMA). 755 18

The aarP gene has been identified in a search for activators of the 2-N-acetyltransferase [encoded by aac(2')-Ia] in Providencia stuartii. Introduction of aarP into P. stuartii on a multicopy plasmid resulted in a 9.9-fold increase in the accumulation of beta-galactosidase from an aac(2')-lacZ fusion. Northern (RNA) blot analysis demonstrated that this increased aac(2')-Ia expression occurred at the level of mRNA accumulation. The deduced AarP protein was 15,898 Da in size and exhibited significant homology to a number of transcriptional activators in the AraC/XyIS family, including TetD,Rob, MarA, and SoxS. The similarity of AarP to the MarA and SoxS proteins prompted an investigation to determine whether AarP is involved in activation of genes in either the multiple antibiotic resistance (Mar) phenotype or redox stress (SoxRS) system. Introduction of aarP on a multicopy plasmid into either P. stuartii or Escherichia coli conferred a Mar phenotype with higher levels of resistance to tetracycline, chloramphenicol, and ciprofloxacin. Multiple copies of aarP in E. coli also resulted in activation of the endonuclease IV gene (nfo), a gene in the SoxRS regulon of E. coli. The function of aarP in its single-copy state was addressed by using allelic replacement to construct an aarP::Cm disruption, which resulted in a fivefold reduction in the accumulation of aac(2')-Ia mRNA. Analysis of aarP regulation showed that aarP mRNA accumulation was slightly increased by exposure to tetracycline and dramatically increased in cells containing the aarB3 (aar3) mutation, which was previously shown to increase transcription of the aac(2')-Ia gene. (P.N. Rather, E. Oroz, K.J. Shaw, R. Hare, and G. Miller, J. Bacteriol. 175:6492-6498).
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PMID:Identification and analysis of aarP, a transcriptional activator of the 2'-N-acetyltransferase in Providencia stuartii. 776 49

The AraC protein, which regulates the L-arabinose operons in Escherichia coli, was dissected into two domains that function in chimeric proteins. One provides a dimerization capability and binds the ligand arabinose, and the other provides a site-specific DNA-binding capability and activates transcription. In vivo and in vitro experiments showed that a fusion protein consisting of the N-terminal half of the AraC protein and the DNA-binding domain of the LexA repressor dimerizes, binds well to a LexA operator, and represses expression of a LexA operator-beta-galactosidase fusion gene in an arabinose-responsive manner. In vivo and in vitro experiments also showed that a fusion protein consisting of the C-terminal half of the AraC protein and the leucine zipper dimerization domain from the C/EBP transcriptional activator binds to araI and activates transcription from a PBAD promoter-beta-galactosidase fusion gene. Dimerization was necessary for occupancy and activation of the wild-type AraC binding site.
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PMID:Functional domains of the AraC protein. 851 13

The lactose utilization genes of Staphylococcus xylosus have been isolated and characterized. The system is comprised of two structural genes, lacP and lacH, encoding the lactose permease and the beta-galactosidase proteins, respectively, and a regulatory gene, lacR, coding for an activator of the AraC/XylS family. The lactose utilization genes are divergently arranged, the lacPH genes being opposite to lacR. The lacPH genes are cotranscribed from one promoter in front of lacP, whereas lacR is transcribed from two promoters of different strengths. Lactose transport as well as beta-galactosidase activity are inducible by the addition of lactose to the growth medium. Primer extension experiments demonstrated that regulation is achieved at the level of lacPH transcription initiation. Inducibility and efficient lacPH transcription are dependent on a functional lacR gene. Inactivation of lacR resulted in low and constitutive lacPH expression. Expression of lacR itself is practically constitutive, since transcription initiated at the major lacR promoter does not respond to the availability of lactose. Only the minor lacR promoter is lactose inducible. Apart from lactose-specific, LacR-dependent control, the lacPH promoter is also subject to carbon catabolite repression mediated by the catabolite control protein CcpA. When glucose is present in the growth medium, lacPH transcription initiation is reduced. Upon ccpA inactivation, repression at the lacPH promoter is relieved. Despite this loss of transcriptional regulation in the ccpA mutant strain, beta-galactosidase activity is still reduced by glucose, suggesting another level of control.
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PMID:Regulation of lactose utilization genes in Staphylococcus xylosus. 957 74

Two types of polyhydroxyalkanoate (PHA) biosynthesis gene loci (phb and pha) of Pseudomonas sp. strain 61-3, which produces a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer (poly(3-hydroxybutyrate-co-3-hydroxyalkanoate) [P(3HB-co-3HA]) consisting of 3HA units of 4 to 12 carbon atoms, were cloned and analyzed at the molecular level. In the phb locus, three open reading frames encoding polyhydroxybutyrate (PHB) synthase (PhbCPs), beta-ketothiolase (PhbAPs), and NADPH-dependent acetoacetyl coenzyme A reductase (PhbBPs) were found. The genetic organization showed a putative promoter region, followed by phbBPs-phbAPs-phbCPs. Upstream from phbBPs was found the phbRPs gene, which exhibits significant similarity to members of the AraC/XylS family of transcriptional activators. The phbRPs gene was found to be transcribed in the opposite direction from the three structural genes. Cloning of phbRPs in a relatively high-copy vector in Pseudomonas sp. strain 61-3 elevated the levels of beta-galactosidase activity from a transcriptional phb promoter-lacZ fusion and also enhanced the 3HB fraction in the polyesters synthesized by this strain, suggesting that PhbRPs is a positive regulatory protein controlling the transcription of phbBACPs in this bacterium. In the pha locus, two genes encoding PHA synthases (PhaC1Ps and PhaC2Ps) were flanked by a PHA depolymerase gene (phaZPs), and two adjacent open reading frames (ORF1 and phaDPs), and the gene order was ORF1, phaC1Ps, phaZPs, phaC2Ps, and phaDPs. Heterologous expression of the cloned fragments in PHA-negative mutants of Pseudomonas putida and Ralstonia eutropha revealed that PHB synthase and two PHA synthases of Pseudomonas sp. strain 61-3 were specific for short chain length and both short and medium chain length 3HA units, respectively.
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PMID:Cloning and molecular analysis of the Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyalkanoate) biosynthesis genes in Pseudomonas sp. strain 61-3. 985 87

The beta-galactosidase-encoding bgaM gene of Bacillus megaterium DSM319 and the divergently orientated bgaR operon were isolated and sequenced. Both traits are subject to catabolite repression. A set of single-gene replacement mutants was generated and used to analyze gene function. BgaR was found to be a XylS/AraC-type positive transcriptional regulator of bgaM; a potential regulator binding site overlaps the bgaM promoter. A mechanism for regulation of beta-galactosidase expression in B. megaterium is proposed.
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PMID:Regulation of beta-galactosidase expression in Bacillus megaterium DSM319 by a XylS/AraC-type transcriptional activator. 1032 36

Expression of Proteus mirabilis urease is governed by UreR, an AraC-like positive transcriptional activator. A poly(A) tract nucleotide sequence, consisting of A(6)TA(2)CA(2)TGGTA(5)GA(6)TGA(5), is located 16 bp upstream of the sigma(70)-like ureR promoter P2. Since poly(A) tracts of DNA serve as binding sites for the gene repressor histone-like nucleoid structuring protein (H-NS), we measured beta-galactosidase activity of wild-type Escherichia coli MC4100 (H-NS(+)) and its isogenic derivative ATM121 (hns::Tn10) (H-NS(-)) harboring a ureR-lacZ operon fusion plasmid (pLC9801). beta-Galactosidase activity in the H-NS(-) host strain was constitutive and sevenfold greater (P < 0.0001) than that in the H-NS(+) host. A recombinant plasmid containing cloned P. mirabilis hns was able to complement and restore repression of the ureR promoter in the H-NS(-) host when provided in trans. Deletion of the poly(A) tract nucleotide sequence from pLC9801 resulted in an increase in beta-galactosidase activity in the H-NS(+) host to nearly the same levels as that observed for wild-type pLC9801 harbored by the H-NS(-) host. Urease activity in strains harboring the recombinant plasmid pMID1010 (encoding the entire urease gene cluster of P. mirabilis) was equivalent in both the H-NS(-) background and the H-NS(+) background in the presence of urea but was eightfold greater (P = 0.0001) in the H-NS(-) background in the absence of urea. We conclude that H-NS represses ureR expression in the absence of urea induction.
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PMID:H-NS is a repressor of the Proteus mirabilis urease transcriptional activator gene ureR. 1076 73

SoxS is the direct transcriptional activator of at least 15 genes of the Escherichia coli superoxide regulon. SoxS is small (107 amino acids), binds DNA as a monomer and recognizes a highly degenerate DNA binding site, termed 'soxbox'. Like other members of the AraC/XylS family, SoxS has two putative helix-turn-helix (HTH) DNA-binding motifs, and it has been proposed that each HTH motif recognizes a highly conserved recognition element of the soxbox. To determine which nucleotides are important for SoxS binding, we conducted a systematic mutagenesis of the DNA binding sites for SoxS in the zwf and fpr promoters and determined the effect of the soxbox mutations on SoxS DNA binding and transcription activation in vivo by measuring beta-galactosidase activity in strains with fusions to lacZ. We found that the sequences GCAC and CAAA, termed recognition elements 1 and 2 (RE 1 and RE 2), respectively, are critical for SoxS binding, as mutations within these elements severely hinder or eliminate SoxS-dependent transcription activation; substitutions within RE 2 (CAAA), however, are tolerated better than changes within RE 1 (GCAC). Although substitutions at the seven positions separating the two REs had only a modest effect on SoxS binding, AT basepairs were favoured within this 'spacer' region, presumably because, by facilitating DNA bending, they help bring the two recognition elements into proper juxtaposition. We also found that the 'invariant A' present at position 1 of 14/15 functional soxboxes identified thus far is important for SoxS binding, as a change to any other nucleotide at this position reduced SoxS-dependent transcription by approximately 50%. In addition, positions surrounding the REs seem to show a context effect, in that certain substitutions there have little or no effect when the RE has the optimal binding sequence, but produce a pronounced effect when the RE has a suboptimal sequence. We propose that these nucleotides play an important role in effecting differential expression from the various promoters. Lastly, we used gel retardation assays to show that alterations in transcription activation in vivo are caused by effects on DNA binding. Based on this exhaustive mutagenesis, we propose the following optimal sequence for SoxS binding: AnVGCACWWWnKRHCAAAHn (n = A, C, G, T; V = A, C, G; W = A, T; K = G, T; R = A, G; H = A, C, T).
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PMID:Systematic mutagenesis of the DNA binding sites for SoxS in the Escherichia coli zwf and fpr promoters: identifying nucleotides required for DNA binding and transcription activation. 1140 18

Transcription activation of anaerobically induced genes in Escherichia coli is mediated through the action of the global anaerobic regulator FNR. Although regions of FNR involved in FNR-dependent transcription activation have been identified, the side-chains critical to the function of these regions are not known. In this study, alanine-scanning of amino acid residues 80-89 of FNR-activating region 3 (FNR-AR3) was used to determine which amino acid side-chains are required for transcription activation of class II FNR-dependent promoters. In vivo beta-galactosidase assays and in vitro transcription activation assays showed that Ala substitution of Ile81, Gly85 and Asp86 had the largest transcription activation defects, while comparison of the activity of single and double mutants indicated that Thr82, Glu83, Glu87 and Gln88 may contribute in a minor way to FNR-AR3 function. Site-directed mutagenesis of positions 81 and 86 showed that the hydrophobicity of Ile81 and the negative charge of Asp86 were important to FNR-AR3's function. Lastly, substitution of residues of E. coli FNR-AR3 with those more basic residues found in a subset of FNR homologs, such as Rhodobacter sphaeroides FnrL, resulted in a mutant strain that was unable to activate transcription from E. coli class II FNR-dependent promoters. In conclusion, this study demonstrates a requirement for negatively charged and hydrophobic side-chain residues in E. coli FNR-AR3 function, although there is likely to be some variability in the characteristics of this region in other members of the FNR family.
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PMID:Characterization of activating region 3 from Escherichia coli FNR. 1178 11

The allosteric mechanism by which the gene expression regulatory protein AraC regulates its DNA-binding activity is shown to be portable by grafting it to beta-galactosidase, generating an arabinose-regulated beta-galactosidase. A portion of the alpha-peptide sequence that complements the activity of alpha-acceptor beta-galactosidase was inserted into a nonessential region of the regulatory peptidyl arm of AraC protein. Arabinose, which regulates the position of the arm in AraC protein now regulates the availability of the alpha-peptide to alpha-acceptor beta-galactosidase, thereby modulating its activity in response to arabinose.
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PMID:A portable allosteric mechanism. 1532 89


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