title: Characterization of Grp1p, a novel cis-Golgi matrix protein.
abstract: A high copy suppressor screen with sec34-2, a temperature-sensitive mutant defective in the late stages of ER to Golgi transport, has resulted in the identification of a novel gene called GRP1 (also called RUD3). GRP1 encodes a hydrophilic yeast protein related to the mammalian Golgi matrix protein golgin-160. A large portion of the protein is predicted to form a coiled-coil structure. Although GRP1 is not essential for growth, the loss of Grp1p results in a growth defect at high temperature. GRP1 genetically interacts with several genes involved in vesicle targeting/fusion stages of ER to Golgi transport. Despite these interactions, pulse chase analysis using Grp1p-depleted cells did not reveal a significant delay in the transit of the vacuolar protease carboxypeptidase Y. Grp1p-depleted cells efficiently secreted invertase which was underglycosylated, suggesting some disturbance of Golgi function. Grp1p-GFP predominantly colocalizes with the cis-Golgi marker Och1p. Despite lacking a signal peptide and a significant stretch of hydrophobic amino acids, Grp1p pellets with membranes. It is extracted with 1M NaCl or 0.1M Na(2)CO(3) (pH 11.0), but is surprisingly insoluble in 1% Triton X-100. Grp1p does not recycle to the ER when forward transport is blocked and a cis-Golgi marker (Och1p-HA), but not a trans-Golgi marker (Chs5p-HA), became dispersed in grp1 Delta cells after 1.5h incubation at 38.5 degrees C. Together, these data suggest that Grp1p is a novel matrix protein that is involved in the structural organization of the cis-Golgi.
authors.affiliation: Howard Hughes Medical Institute and the Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA. dwkim@mclean.harvard.edu
authors.forename: Dong-Wook
authors.initials: DW
authors.lastname: Kim
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008364:Mannosyltransferases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics*; D008856:Microscopy, Fluorescence; D017830:Octoxynol / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D013347:Subcellular Fractions; D013696:Temperature; D013997:Time Factors; D033921:Vesicular Transport Proteins; D043324:beta-Fructofuranosidase
chemical_list: D002352:Carrier Proteins; D003902:Detergents; D008164:Luminescent Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C075636:OCH1 protein, S cerevisiae; D010455:Peptides; C400547:RUD3 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D017830:Octoxynol; D008364:Mannosyltransferases; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase