Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:O95477 (membrane-bound)
 29,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A full-length E(ecto)-ATPase (Plesner, L. (1995) Int. Rev. Cytol. 158, 141-214) cDNA was cloned from a human brain cDNA library; it encodes a 610-amino acid protein that contains two putative transmembrane domains. Heterologous expression of this protein in COS-7 cells caused a significant increase in intracellular membrane-bound nucleoside phosphatase activity. The activity was highest with UDP as substrate and was stimulated by divalent cations in the following order: Ca2+ >> Mg2+ > Mn2+. The results of immunofluorescence staining indicate that this protein is located in the Golgi apparatus. UDP hydrolysis was increased in the presence of Triton X-100 or alamethicin, an ionophore that facilitates movement of UDP across the membrane, suggesting that the active site of this UDPase is on the luminal side of the Golgi apparatus. This is the first identification of a mammalian Golgi luminal UDPase gene. Computer-aided sequence analysis of the EATPase superfamily indicates that the human UDPase is highly similar to two hypothetical proteins of the nematode Caenorhabditis elegans and to an unidentified 71.9-kDa yeast protein and is less related to the previously identified yeast Golgi GDPase.
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PMID:Golgi localization and functional expression of human uridine diphosphatase. 955 35

The gene for the open reading frame YER005w that is homologous to yeast Golgi GDPase encoded by the GDA1 gene was cloned and named YND1. It encodes a 630-amino acid protein that contains a single transmembrane region near the carboxyl terminus. The overexpression of the YND1 gene in the gda1 null mutant caused a significant increase in microsomal membrane-bound nucleoside phosphatase activity with a luminal orientation. The activity was equally high toward ADP/ATP, GDP/GTP, and UDP/UTP and approximately 50% less toward CDP/CTP and thiamine pyrophosphate, but there was no activity toward GMP, indicating that the Ynd1 protein belongs to the apyrase family. This substrate specificity is different from that of yeast GDPase, but similar to that of human Golgi UDPase. The Deltaynd1 mutant cells were defective in O- and N-linked glycosylation in the Golgi compartments. The overexpression of the YND1 gene complemented some glycosylation defects in Deltagda1 disruptants, suggesting a partially redundant function of yeast apyrase and GDPase. From these results and the phenotype of the Deltaynd1Deltagda1 double deletion showing a synthetic effect, we conclude that yeast apyrase is required for Golgi glycosylation and cell wall integrity, providing the first direct evidence for the in vivo function of intracellular apyrase in eukaryotic cells.
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PMID:YND1, a homologue of GDA1, encodes membrane-bound apyrase required for Golgi N- and O-glycosylation in Saccharomyces cerevisiae. 1040 9

The molecular mechanisms regulating hemicelluloses and pectin biosynthesis are poorly understood. An important question in this regard is how glycosyltransferases are oriented in the Golgi cisternae, and how nucleotide sugars are made available for the synthesis of the polymers. Here we show that the branching enzyme xyloglucan alpha,1-2 fucosyltransferase (XG-FucTase) from growing pea (Pisum sativum) epicotyls was latent and protected against proteolytic inactivation on intact, right-side-in pea stem Golgi vesicles. Moreover, much of the XG-FucTase activity was membrane associated. These data indicate that XG-FucTase is a membrane-bound luminal enzyme. GDP-Fuc uptake studies demonstrated that GDP-Fuc was taken up into Golgi vesicles in a protein-mediated process, and that this uptake was not competed by UDP-Glc, suggesting that a specific GDP-Fuc transporter is involved in xyloglucan biosynthesis. Once in the lumen, Fuc was transferred onto endogenous acceptors, including xyloglucan. GDPase activity was detected in the lumen of the vesicles, suggesting than the GDP produced upon transfer of Fuc was hydrolyzed to GMP and inorganic phosphate. We suggest than the GDP-Fuc transporter and GDPase may be regulators of xyloglucan fucosylation in the Golgi apparatus from pea epicotyls.
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PMID:GDP-fucose uptake into the Golgi apparatus during xyloglucan biosynthesis requires the activity of a transporter-like protein other than the UDP-glucose transporter. 1071 51