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)

A plasmid-encoding fusion protein interlinked by factor Xa recognition sequence between beta-galactosidase and a precursor of the small subunit of wheat ribulose-1,5-bisphosphate carboxylase has been constructed. The plasmid directed abundant synthesis of the fusion protein in Escherichia coli. The recombinant protein was accumulated in an aggregated form that was associated with the bacterial membranes. A procedure was developed to isolate the fusion protein in a relatively pure and soluble form. Bovine factor Xa cleaved the isolated chimera to generate the complete chloroplast precursor of the small subunit of ribulose-1,5-bisphosphate carboxylase from the fused beta-galactosidase. The cleaved precursor protein was imported into the isolated chloroplasts and processed to yield its mature counterpart.
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PMID:An import-competent precursor of small subunit of ribulose-1,5-bisphosphate carboxylase generated by factor Xa cleavage from a beta-galactosidase fusion expressed in Escherichia coli. 139 14

The hydrophobic-rich NH2-terminal 34 amino acids of a tetracycline resistance determinant (TetC) were fused to the COOH-terminal 240 amino acids of the hemolysin transporter, HlyB, which contains a putative ATP-binding domain. This hybrid protein replaced the NH2-terminal 467-amino-acid portion of HlyB and could still export the Escherichia coli hemolysin (HlyA). Export by the hybrid protein was approximately 10% as efficient as transport by HlyB. Extracellular secretion of HlyA by the TetC-HlyB hybrid required HlyD and TolC. The extracellular and periplasmic levels of beta-galactosidase and beta-lactamase in strains that produced the hybrid were similar to the levels in controls. Thus, HlyA transport was specific and did not appear to be due to leakage of cytoplasmic contents alone. Antibodies raised against the COOH terminus of HlyB reacted with the hybrid protein, as well as HlyB. HlyB was associated with membrane fractions, while the hybrid protein was found mainly in soluble extracts. Cellular fractionation studies were performed to determine whether transport by the hybrid occurred simultaneously across both membranes like wild-type HlyA secretion. However, we found that HlyA was present in the periplasm of strains that expressed the TetC-HlyB hybrid. HlyA remained in the periplasm unless the hlyD and tolC gene products were present in addition to the hybrid.
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PMID:A heterologous membrane protein domain fused to the C-terminal ATP-binding domain of HlyB can export Escherichia coli hemolysin. 140 Feb 27

Three members of the Src family of tyrosine kinases [pp60c-src (Src), p59fyn (Fyn) and pp62c-yes (Yes)] are ubiquitously expressed, and are thus likely to have general roles in growth control. We have previously shown that, after addition of platelet-derived growth factor (PDGF) to quiescent cells, all three kinases become activated and associated with the PDGF receptor. We have now addressed the requirements for this association. First, we have used a baculovirus expression system to show that Fyn associates with the activated PDGF receptor in vitro in the absence of other proteins, demonstrating that the association between the two molecules is direct. Second, by generating cell lines expressing chimeric molecules consisting of Fyn sequences fused to a portion of beta-galactosidase, we found that the SH2 domain of Fyn is necessary for ligand-stimulated association with the PDGF receptor in vivo. Third, those fusion proteins that associated with the PDGF receptor also became phosphorylated in vivo following PDGF treatment, and in in vitro kinase assays, suggesting that the amino-terminal half of Fyn contains the sites of PDGF-stimulated phosphorylation. Partially purified, kinase-negative Fyn also became phosphorylated in the activated PDGF receptor complex in vitro, demonstrating that the PDGF receptor phosphorylates Fyn, rather than the novel phosphorylations occurring by autophosphorylation.
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PMID:Association of Fyn with the activated platelet-derived growth factor receptor: requirements for binding and phosphorylation. 140 31

Tissue-specific patterns of methylated deoxycytidine residues in the mammalian genome are preserved by postreplicative methylation of newly synthesized DNA. DNA methyltransferase (MTase) is here shown to associate with replication foci during S phase but to display a diffuse nucleoplasmic distribution in non-S phase cells. Analysis of DNA MTase-beta-galactosidase fusion proteins has shown that association with replication foci is mediated by a novel targeting sequence located near the N-terminus of DNA MTase. This sequence has the properties expected of a targeting sequence in that it is not required for enzymatic activity, prevents proper targeting when deleted, and, when fused to beta-galactosidase, causes the fusion protein to associate with replication foci in a cell cycle-dependent manner.
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PMID:A targeting sequence directs DNA methyltransferase to sites of DNA replication in mammalian nuclei. 142 34

The effect of heat shock on the expression of some genes of Escherichia coli was tested. To avoid side effects, promoters of the genes were fused to lacZ and their expression measured by the level of beta-galactosidase. The results show that expression of umuC, recA and polB, after induction of the SOS response, was somewhat higher in the heat-shocked than in the non-shocked cells, whereas expression of ada, alkB and alkA genes, after induction of the adaptive response, was about the same. Unexpectedly, it was found that expression of lacZ from its own promoter was drastically lowered in the heat-shocked cells. This effect, however, seems not to be dependent on the induction of heat-shock proteins.
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PMID:Effect of heat shock on expression of proteins not involved in the heat-shock regulon. 142 61

The central region of the N-myc protein has a characteristic amino acid sequence EDTLSDSDDEDD, which is very similar to those of particular domains of adenovirus E1A, human papilloma virus E7, Simian virus 40 large T, c-myc and L-myc proteins. Domains of these three viral oncoproteins have recently been shown to be specific binding sites for the tumor-suppressor gene retinoblastoma protein. We have noted that the sequence of serine followed by a cluster of acidic amino acids is exactly the same as that of a typical substrate of casein kinase II (CKII). Therefore, we investigated whether these nuclear oncoproteins are phosphorylated by CKII. For this purpose, we fused the beta-galactosidase and N-myc genes including this domain and expressed it in Escherichia coli cells. Several mutant N-myc genes, containing single amino acid substitutions in this domain, were also used to produce fused proteins. Strong phosphorylation by CKII was detected with the fused protein of wild-type N-myc. However, no phosphorylation of beta-galactosidase itself was observed and the phosphorylations of fused mutant proteins were low. Another fused N-myc protein containing most of the C-terminal region downstream of this acidic region was not phosphorylated by CKII. Analysis of phosphorylation sites in synthetic peptides of this acidic region identified the major sites phosphorylated by CKII as Ser261 and Ser263. On two-dimensional tryptic mapping of phosphorylated N-myc proteins, major spots of in vitro-labeled and in-vivo-labeled N-myc proteins were detected in the same positions. These results suggest that two serine residues of the acidic central region of the N-myc protein are phosphorylated by CKII in vivo as well as in vitro. The functional significance of this acidic domain is discussed.
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PMID:Specific phosphorylation of the acidic central region of the N-myc protein by casein kinase II. 142 1

The transcription of the luminescence (lux) system of Vibrio fischeri is regulated by the LuxR protein and an autoinducer. We previously showed that apart from these regulatory elements, the transcription of the lux system is negatively controlled by the LexA protein and positively controlled by the HtpR protein (sigma 32). This study was conducted in order to elucidate the mode of action of the HtpR protein. Using luxR-lacZ fused genes, we showed that the HtpR protein is essential for the maximum expression of beta-galactosidase activity in Escherichia coli lac mutant cells. Using this construct, we also demonstrated that luxR is preferentially expressed toward the end of the logarithmic phase of growth. Starvation and addition of ethanol significantly advanced the appearance of beta-galactosidase activity in htpR+ cells. The luminescence system of E. coli htpR+ cells harboring the pChv1 plasmid with a deletion in the luxI gene is induced in the presence of low and constant concentrations (150 pg/ml) of the inducer only at a late stage of the logarithmic phase of growth. When the cellular LuxR content is reduced, following 23 generations of exponential growth in Luria broth, a mid-log-phase culture does not respond to the inducer (150 pg/ml). On the basis of the above observations we suggest that the HtpR protein controls the formation of V. fischeri LuxR protein. Preliminary findings indicate that the HtpR protein acts through the chaperonins GroESL. E. coli htpR/pChv1 cells retained their full level of in vivo and in vitro luciferase activities in the presence of multiple copies of groESL genes. The possibility that GroESL proteins stabilize the native form of LuxR protein is discussed.
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PMID:Formation of the LuxR protein in the Vibrio fischeri lux system is controlled by HtpR through the GroESL proteins. 142 36

The regulation of Shiga toxin expression in a clinical isolate of S. dysenteriae 1 by the Fe-Fur (Iron-ferric uptake regulatory protein) repressor complex was investigated. The presence of an endogenous Fur repressor protein capable of binding to either a Fur binding consensus sequence or the regulatory region of SLT-1A was determined in toxinogenic strains of S. dysenteriae. Plasmid constructs bearing Fur binding sites fused to readily assayable reporter genes were used. Plasmid pSC27.1 contains a 21 bp synthetic oligonucleotide Fur protein binding consensus sequence located upstream to the gene for beta-galactosidase. Plasmid pSC105 contains the regulatory sequences of Shiga-like toxin-1A located upstream to the gene for alkaline phosphatase. In an analogous fashion to Shiga toxin regulation in S. dysenteriae 1, transformants bearing either pSC27.1 or pSC105 plasmid DNA were repressed in gene product expression when grown in minimal medium supplemented with iron. Conversely, transformants were de-repressed when grown under iron limiting conditions. These data suggest the presence of Fe-Fur mediated regulation of toxinogenesis in clinical isolates of S. dysenteriae.
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PMID:Regulation of the SLT-1A toxin operon by a ferric uptake regulatory protein in toxinogenic strains of Shigella dysenteriae type 1. 143 Sep 67

Five open reading frames designated nirB, nirD, nirE, nirC and cysG have been identified from the DNA sequence of the Escherichia coli nir operon. Complementation experiments established that the NirB, NirD and CysG polypeptides are essential and sufficient for NADH-dependent nitrite reductase activity (EC 1.6.6.4). A series of plasmids has been constructed in which each of the open reading frames has been fused in-phase with the beta-galactosidase gene, lacZ. Rates of beta-galactosidase synthesis during growth in different media revealed that nirB, -D, -E and -C are transcribed from the FNR-dependent promoter, p-nirB, located just upstream of the nirB gene: expression is co-ordinately repressed by oxygen and induced during anaerobic growth. Although the nirB, -D and -C open reading frames are translated into protein, no translation of nirE mRNA was detected. The cysG gene product is expressed from both p-nirB and a second, FNR-independent promoter, p-cysG, located within the nirC gene. No NADH-dependent nitrite reductase activity was detected in extracts from bacteria lacking either NirB or NirD, but a mixture of the two was as active as an extract from wild-type bacteria. Reconstitution of enzyme activity in vitro required stoichiometric quantities of NirB and NirD and was rapid and independent of the temperature during mixing. NirD remained associated with NirB during the initial stages of purification of the active enzyme, suggesting that NirD is a second structural subunit of the enzyme.
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PMID:Transcriptional control, translation and function of the products of the five open reading frames of the Escherichia coli nir operon. 143 59

The activity of p21ras is required for the proliferative response to colony-stimulating factor 1 (CSF-1), and signals transduced by both the CSF-1 receptor (CSF-1R) and p21ras stimulate transcription from promoter elements containing overlapping binding sites for Fos/Jun- and Ets-related proteins. A sequence encoding the DNA-binding domain and nuclear localization signal of human c-ets-2, which lacked portions of the c-ets-2 gene product necessary for trans activation, was fused to the bacterial lacZ gene and expressed from an actin promoter in NIH 3T3 cells expressing either the v-ras oncogene or human CSF-1R. Nuclear expression of the Ets-LacZ protein, confirmed by histochemical staining of beta-galactosidase, inhibited the activity of ras-responsive enhancer elements and suppressed morphologic transformation by v-ras as well as CSF-1R-dependent colony formation in semisolid medium. When CSF-1R-bearing cells expressing the Ets-LacZ protein were stimulated by CSF-1, induction of c-ets-2, c-jun, and c-fos ensued, but the c-myc response was impaired. Enforced expression of the c-myc gene overrode the suppressive effect of ets-lacZ and restored the ability of these cells to form colonies in response to CSF-1. NIH 3T3 cells engineered to express a CSF-1R (Phe-809) mutant similarly cannot form CSF-1-dependent colonies in semisolid medium and exhibit an impaired c-myc response, but expression of an exogenous myc gene resensitizes these cells to CSF-1 [M. F. Roussel, J. L. Cleveland, S. A. Shurtleff, and C. J. Sherr, Nature (London) 353:361-363, 1991]. The ability of these cells to respond to CSF-1 was also rescued by enforced expression of an endogenous c-ets-2 gene. The ets family of transcription factors therefore plays a central role in integrating both CSF-1R and ras-induced mitogenic signals and in modulating the myc response to CSF-1 stimulation.
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PMID:Mitogenic signaling by colony-stimulating factor 1 and ras is suppressed by the ets-2 DNA-binding domain and restored by myc overexpression. 144 70


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