SQV-7, a protein involved in Caenorhabditis elegans epithelial invagination and early embryogenesis, transports UDP-glucuronic acid, UDP-N- acetylgalactosamine, and UDP-galactose.
Caenorhabditis elegans sqv mutants are defective in vulval epithelial invagination and have a severe reduction in hermaphrodite fertility. The gene sqv-7 encodes a multitransmembrane hydrophobic protein resembling nucleotide sugar transporters of the Golgi membrane. A Golgi vesicle enriched fraction of Saccharomyces cerevisiae expressing SQV-7 transported UDP-glucuronic acid, UDP-N-acetylgalactosamine, and UDP-galactose (Gal) in a temperature-dependent and saturable manner. These nucleotide sugars are competitive, alternate, noncooperative substrates. The two mutant sqv-7 missense alleles resulted in a severe reduction of these three transport activities. SQV-7 did not transport CMP-sialic acid, GDP-fucose, UDP-N-acetylglucosamine, UDP-glucose, or GDP-mannose. SQV-7 is able to transport UDP-Gal in vivo, as shown by its ability to complement the phenotype of Madin-Darby canine kidney ricin resistant cells, a mammalian cell line deficient in UDP-Gal transport into the Golgi. These results demonstrate that unlike most nucleotide sugar transporters, SQV-7 can transport multiple distinct nucleotide sugars. We propose that SQV-7 translocates multiple nucleotide sugars into the Golgi lumen for the biosynthesis of glycoconjugates that play a pivotal role in development.
Berninsone
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Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA.
Hwang
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Zemtseva
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Horvitz
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Hirschberg
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CB
D000818:Animals; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000196:embryology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D004285:Dogs; D004351:Drug Resistance; D004847:Epithelial Cells / Q000502:physiology; D009004:Monosaccharide Transport Proteins; D033701:Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins; D012441:Saccharomyces cerevisiae; D013347:Subcellular Fractions; D014162:Transfection; D014531:Uridine Diphosphate Galactose / Q000378:metabolism*; D014535:Uridine Diphosphate Glucuronic Acid / Q000378:metabolism*; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D009004:Monosaccharide Transport Proteins; D033701:Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins; C414738:sqv-7 protein, C elegans; D014535:Uridine Diphosphate Glucuronic Acid; D014531:Uridine Diphosphate Galactose; D014536:Uridine Diphosphate N-Acetylgalactosamine