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)

Prosaposin, the precursor of saposins A, B, C, and D, which activate lysosomal hydrolysis of sphingolipids, exists in various tissues and body fluids and is especially abundant in the nervous system. Prosaposin and saposins A,B, C, and D formed stable complexes with 13 different gangliosides as measured by an assay using column chromatography. Gangliosides of the gangliotetraose type (a series) were bound with high affinity, whereas b series gangliosides, O-acetylated gangliosides, and gangliosides with shorter carbohydrate chains, were bound with lower affinity. Prosaposin and saposins transferred gangliosides from donor liposomes to erythrocyte ghost membranes. Prosaposin also stimulated ganglioside GM1 beta-galactosidase more than mature saposins. Prosaposin exists as a secretory protein and as an integral membrane protein, and we propose that prosaposin is active as a ganglioside binding and transport protein in vivo.
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PMID:Binding and transport of gangliosides by prosaposin. 145 4

A 2.3-kb genomic clone has been isolated from the region where the tissue-specific puff, Balbiani ring a (BRa), is found on chromosome IV of the special lobe of Chironomus thummi salivary gland cells. The clone was characterized by nucleotide sequence analysis. Two clusters of direct tandem repeats were identified, as well as large and small open reading frames (ORFs). The large ORF was fused to an Escherichia coli lacZ gene. Antibodies against the beta-galactosidase/ORF fusion protein reacted selectively on Western blots with a 67-kDa protein. Western-blot analysis and immunoelectron microscopy showed that this protein was distributed in the cells of all larval tissues examined. We concluded that BRa, a tissue-specific puff, whose activity correlates with the synthesis of 160-kDa secretory protein [Kolesnikov et al., Chromosoma 83 (1981) 661-677], may also contain a gene which is not expressed in a tissue-specific manner.
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PMID:A tissue-specific puff (Balbiani ring a) in Chironomus thummi may contain a gene encoding a 67-kDa protein which exhibits non-tissue-specific expression. 226 33

SEC18 gene function is required for secretory protein transport between the endoplasmic reticulum (ER) and the Golgi complex. We cloned the SEC18 gene by complementation of the sec18-1 mutation. Gene disruption has shown that SEC18 is essential for yeast cell growth. Sequence analysis of the gene revealed a 2,271-base-pair open reading frame which could code for a protein of 83.9 kilodaltons. The predicted protein sequence showed no significant similarity to other known protein sequences. In vitro transcription and translation of SEC18 led to the synthesis of two proteins of approximately 84 and 82 kilodaltons. Antisera raised against a Sec18-beta-galactosidase fusion protein also detected two proteins (collectively referred to as Sec18p) in extracts of 35S-labeled yeast cells identical in size to those seen by in vitro translation. Mapping of the 5' end of the SEC18 mRNA revealed only one major start site for transcription, which indicates that the multiple forms of Sec18p do not arise from mRNAs with different 5' ends. Results of pulse-chase experiments indicated that the two forms of Sec18p are not the result of posttranslational processing. We suggest that translation initiating at different in-frame AUG start codons is likely to account for the presence of two forms of Sec18p. Hydrophobicity analysis indicated that the proteins were hydrophilic in nature and lacked any region that would be predicted to serve as a signal sequence or transmembrane anchor. Although potential sites for N-linked glycosylation were present in the Sec18p sequence, the sizes of the in vivo SEC18 gene products were unaffected by the drug tunicamycin, indicating that Sec18p does not enter the secretory pathway. These results suggest that Sec18p resides in the cell cytoplasm. While preliminary cell fractionation studies showed that Sec18p is not associated with the ER or Golgi complex, association with a 100,000 x g pellet fraction was observed. This suggests that Sec18p may bind transiently to small vesicles such as those presumed to participate in secretory protein transport between ER and the Golgi complex.
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PMID:Characterization of a component of the yeast secretion machinery: identification of the SEC18 gene product. 305 9

The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.
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PMID:The map of chromosome 20. 307 44

The yeast SUC2 gene codes for the secreted enzyme invertase. A series of 16 different-sized gene fusions have been constructed between this yeast gene and the Escherichia coli lacZ gene, which codes for the cytoplasmic enzyme beta-galactosidase. Various amounts of SUC2 NH2-terminal coding sequence have been fused in frame to a constant COOH-terminal coding segment of the lacZ gene, resulting in the synthesis of hybrid invertase-beta-galactosidase proteins in Saccharomyces cerevisiae. The hybrid proteins exhibit beta-galactosidase activity, and they are recognized specifically by antisera directed against either invertase or beta-galactosidase. Expression of beta-galactosidase activity is regulated in a manner similar to that observed for invertase activity expressed from a wild-type SUC2 gene: repressed in high-glucose medium and derepressed in low-glucose medium. Unlike wild-type invertase, however, the invertase-beta-galactosidase hybrid proteins are not secreted. Rather, they appear to remain trapped at a very early stage of secretory protein transit: insertion into the endoplasmic reticulum (ER). The hybrid proteins appear only to have undergone core glycosylation, an ER process, and do not receive the additional glycosyl modifications that take place in the Golgi complex. Even those hybrid proteins containing only a short segment of invertase sequences at the NH2 terminus are glycosylated, suggesting that no extensive folding of the invertase polypeptide is required before initiation of transmembrane transfer. beta-Galactosidase activity expressed by the SUC2-lacZ gene fusions cofractionates on Percoll density gradients with ER marker enzymes and not with other organelles. In addition, the hybrid proteins are not accessible to cell-surface labeling by 125I. Accumulation of the invertase-beta-galactosidase hybrid proteins within the ER does not appear to confer a growth-defective phenotype to yeast cells. In this location, however, the hybrid proteins and the beta-galactosidase activity they exhibit could provide a useful biochemical tag for yeast ER membranes.
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PMID:Invertase beta-galactosidase hybrid proteins fail to be transported from the endoplasmic reticulum in Saccharomyces cerevisiae. 644 5

A sensitive two-site enzyme immunoassay (EIA) system was established for human pS2 protein, a small estrogen-inducible secretory protein of unknown function originally identified in MCF-7 human breast cancer cells. Our EIA system is based on the sandwiching of antigen between anti-recombinant (r) pS2 antibody IgG coated on a polystyrene plate and biotinylated anti-rpS2 antibody IgG. The amount of pS2 protein was quantified by measurement of the bound enzyme activity of subsequently added streptavidin-linked beta-D-galactosidase (beta-D-galactosidase, EC 3.2.1.23). pS2 protein purified from MCF-7 culture supernatants was detectable at a concentration as low as 3 pg/ml (corresponding to 60 fg/well). This EIA system revealed that the amount of pS2-like immunoreactivity (LI) in human urine was 13.6 ng/mg creatinine (median, n = 416) and that there was no correlation between the pS2-LI concentration in urine and sex or aging. pS2-LI levels in plasma and sera of the normal subjects were 392 pg/ml (median, n = 14) and 494 pg/ml (median, n = 12), respectively. The serum level of the patients with breast cancer (528 pg/ml; median, n = 67) was not statistically different from that of normal subjects, although high levels of pS2 protein in breast cancer tissues had been reported.
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PMID:Estimation of pS2 protein level in human body fluids by a sensitive two-site enzyme immunoassay. 798 37

Prosaposin contains separate domains in tandem for four saposins, A, B, C, and D. These mature saposins are produced by limited proteolysis of prosaposin. They are involved in lysosomal hydrolysis of GM1 ganglioside, gluco- and galactocerebrosides, sulfatides, and sphingomyelin and other sphingolipids. Prosaposin also exists as a secretory protein in body fluids. In this investigation prosaposin was expressed in Spodoptera frugiperda cells (Sf9) by infection with baculovirus containing a full length cDNA coding for human prosaposin. Prosaposin was isolated and purified from spent culture medium of the recombinant Sf9 cell cultures as well as from human seminal plasma and milk. From sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of both native human prosaposins is estimated to be 66 kDa and that of recombinant prosaposin as 58 kDa. Deglycosylation of native and recombinant prosaposins yielded a protein with a molecular weight of 54 kDa and isoelectric point of 5.4. The N-terminal sequence of both native and recombinant prosaposins was identical (G-P-V-L-L-G-L-K). Like mature saposins, all prosaposins possessed stimulative activity for cerebroside beta-glucosidase (saposins A and C activity), GM1 ganglioside beta-galactosidase (saposin B activity), and sphingomyelinase (saposin D activity) but not sulfatide sulfatase (saposin B activity). Partially proteolyzed products derived from prosaposins were isolated and identified. From seminal plasma, two proteins of 48 and 29 kDa and from Sf9 culture media, two proteins of 39 and 26 kDa were characterized. N-terminal amino acid sequencing and Western blot analysis of each protein indicated that the 39-and 48-kDa proteins are cleavage products containing domains for saposins B, C, and D (trisaposins), and the 26- and 29-kDa proteins are cleavage products containing domains for saposins C and D (disaposin). These observations suggest that proteolysis of prosaposin in these tissues occurs sequentially from the N-terminal region. Proteins involved in the initial proteolysis of prosaposin were partially characterized in human testis.
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PMID:Isolation, characterization, and proteolysis of human prosaposin, the precursor of saposins (sphingolipid activator proteins). 832 76

The cysteine-rich trefoil motif of rat intestinal trefoil factor (rITF) was cloned and expressed in Escherichia coli. A 270-bp cDNA fragment including the signal sequence and the trefoil motif was cloned into the expression vector pAX5+ to direct the expression of a beta-galactosidase collagen-hinged fusion protein in E. coli. Cultures harbouring the recombinant plasmid produced a soluble novel protein with a molecular mass of 134.5 kDa, as predicted for the trefoil-motif-containing fusion protein. Purification of the rITF moiety was achieved by p-aminophenyl-thio-beta-D-galactoside(APTG)-affinity chromatography, collagenase digestion of the hybrid molecule, and removal of the beta-galactosidase-hinge molecule by a further APTG-affinity step. It was demonstrated that intrachain disulphide-bond formation in rITF occurred during the procedure, so no refolding steps were required. Analysis by immunoblotting revealed that the fusion protein and the cleaved trefoil-motif-containing protein were recognised by an antibody raised against the chemically synthesised peptide. The trefoil motif present in the fusion protein was used to localise putative trefoil-binding sites in sections of frozen rat tissue. Binding was demonstrated using the beta-galactosidase portion of the fusion protein as a reporter moiety, either directly with 5-bromo-4-chloro-3-indolyl-beta-D-galactoside, or indirectly using a monoclonal antibody to beta-galactosidase and indirect immunohistochemistry. Binding sites were localised to the foveolar and surface epithelium of rat stomach, the collecting ducts of the kidney and within colonic crypts. The presence of a trefoil motif was necessary for binding. The use of beta-galactosidase fusion proteins for histochemical localisation of peptide-binding sites should prove more generally useful.
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PMID:Expression and purification of a trefoil peptide motif in a beta-galactosidase fusion protein and its use to search for trefoil-binding sites. 844 92

The adaptation and application of the Escherichia coli T7 RNA polymerase system for regulated and promoter-specific gene expression in Bacillus subtilis is reported. The expression cassette used in Bacillus subtilis was tightly regulated and T7 RnA polymerase (T7 RNAP)appeared 30 minutes after induction. The efficiency of T7 promoter-specific gene expression in B.subtilis was studied using one secretory and two cytosolic proteins of heterologous origin. The accumulation of E. coli beta-galactosidase, as well as a 1,4-beta-glucosidase from Thermoanaerobacter brockii in B. subtilis after T7 RNAP induction was strongly enhanced by rifampicin inhibition of host RNAP activity. The alpha-amylase of Thermactinomyces vulgaris, a secretory protein, was found to accumulate in the culture supernatant up to levels of about 70 mg/l 10-20 h after T7 RNAP induction, but was also deposited in cellular fractions. The addition of rifampicin inhibited chi-amylase secretion, but unexpectedly, after a short period, also prevented its further (intra)cellular accumulation.
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PMID:A T7 promoter-specific, inducible protein expression system for Bacillus subtilis. 862 23

New secretory signals and strategies can be attempted to improve the secretion of heterologous proteins of biotechnological interest which encounter difficulties being exported in yeast. The GGPI gene of Saccharomyces cerevisiae codes for a 125 kDa glycoprotein transported through the secretory pathway and anchored to the plasma membrane by means of a glycosylphosphatidylinositol. The regions coding for the secretory signal or also for the first 46 amino acids were tested for efficiency in secretion by fusion to the lacZ gene of Escherichia coli resulting in the synthesis of the endoplasmic reticulum-targeted 1-22- and 1-68-GgpIp/beta-gal hybrids. A cytoplasmic form was also examined. The 1-22 beta gal is partially transported to the cell surface and in the medium in an unglycosylated form. The 1-68 beta gal is completely retained in the intracellular membranes and is N-glycosylated in the GgpIp moiety. The amount of hybrid protein produced is similar and independent from its targeted site, suggesting that translocation through endoplasmic reticulum is not a limiting step, whereas the amount of active enzyme is from 50 to 80% lower for the endoplasmic reticulum forms compared with the cytoplasmic form. BiP/Kar2p putative precursor is accumulated in cells expressing the endoplasmic reticulum-targeted forms but not in those producing the cytosolic beta-galactosidase or over-expressing an endogenous secretory protein. Thus, glycosylation and abnormal folding rather than over-expression are among the factors responsible for the decreased activity and exit of beta-galactosidase from the endoplasmic reticulum and for induction of BiP. The results obtained indicate that the sole secretory signal of GgpIp is suitable to drive secretion of foreign products with complex folding and point to the importance of the endoplasmic reticulum quality control in the secretion of heterologous proteins in yeast.
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PMID:Expression and secretion of beta-galactosidase in Saccharomyces cerevisiae using the signal sequences of GgpI, the major yeast glycosylphosphatidylinositol-containing protein. 956 2


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