title: The TIP1 gene of Saccharomyces cerevisiae encodes an 80 kDa cytoplasmic protein that interacts with the cytoplasmic domain of Sec20p.
abstract: The SEC20 gene of Saccharomyces cerevisiae encodes a 50 kDa type II integral membrane glycoprotein that is required for endoplasmic reticulum (ER) to Golgi transport. Here, we have used a genetic screen, based on the lethal effect of overexpressing the cytoplasmic domain of Sec20p, to identify a novel cytosolic factor that interacts with SEC20. This factor is an 80 kDa cytoplasmic protein encoded by the TIP1 (SEC twenty interacting protein) gene. Coimmunoprecipitation and immunofluorescence using Tip1p and Sec20p or its cytoplasmic domain showed that the two proteins physically interact to form a stable complex. Like SEC20, TIP1 is required for ER to Golgi transport and depletion of Tip1p results in accumulation of an extensive network of ER plus small transport vesicles. We therefore propose that Sec20p and Tip1p act together as a functional unit in the ER to Golgi transport step.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Sweet
authors.forename: H R
authors.initials: HR
authors.lastname: Pelham
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004271:DNA, Fungal; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D006023:Glycoproteins; D006056:Golgi Apparatus / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D050766:Qb-SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D050766:Qb-SNARE Proteins; C073173:SEC20 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C489479:TIP20 protein, S cerevisiae; D033921:Vesicular Transport Proteins