Specific binding to a novel and essential Golgi membrane protein (Yip1p) functionally links the transport GTPases Ypt1p and Ypt31p.
The regulation of vesicular transport in eukaryotic cells involves Ras-like GTPases of the Ypt/Rab family. Studies in yeast and mammalian cells indicate that individual family members act in vesicle docking/fusion to specific target membranes. Using the two-hybrid system, we have now identified a 248 amino acid, integral membrane protein, termed Yip1, that specifically binds to the transport GTPases Ypt1p and Ypt31p. Evidence for physical interaction of these GTPases with Yip1p was also demonstrated by affinity chromatography and/or co-immunoprecipitation. Like the two GTPases, Yip1p is essential for yeast cell viability and, according to subcellular fractionation and indirect immunofluorescence, is located to Golgi membranes at steady state. Mutant cells depleted of Yip1p and conditionally lethal yip1 mutants at the non-permissive temperature massively accumulate endoplasmic reticulum membranes and display aberrations in protein secretion and glycosylation of secreted invertase. The results suggests for a role for Yip1p in recruiting the two GTPases to Golgi target membranes in preparation for fusion.
Max Planck Institute for Biophysical Chemistry, Department of Molecular Genetics, D-37070 Göttingen, Germany.
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Gallwitz
D000595:Amino Acid Sequence; D001692:Biological Transport; D002451:Cell Compartmentation; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013347:Subcellular Fractions; D020691:rab GTP-Binding Proteins
D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; C087905:YPT31 protein, S cerevisiae; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C060755:YPT1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins