Got1p and Sft2p: membrane proteins involved in traffic to the Golgi complex.
Traffic through the yeast Golgi complex depends on a member of the syntaxin family of SNARE proteins, Sed5p, present in early Golgi cisternae. Sft2p is a non-essential tetra-spanning membrane protein, found mostly in the late Golgi, that can suppress some sed5 alleles. We screened for mutations that show synthetic lethality with sft2 and found one that affects a previously uncharacterized membrane protein, Got1p, as well as new alleles of sed5 and vps3. Got1p is an evolutionarily conserved non-essential protein with a membrane topology similar to that of Sft2p. Immunofluorescence and subcellular fractionation indicate that it is present in early Golgi cisternae. got1 mutants, but not sft2 mutants, show a defect in an in vitro assay for ER-Golgi transport at a step after vesicle tethering to Golgi membranes. In vivo, inactivation of both Got1p and Sft2p results in phenotypes ascribable to a defect in endosome-Golgi traffic, while their complete removal results in an ER-Golgi transport defect. Thus the presence of either Got1p or Sft2p is required for vesicle fusion with the Golgi complex in vivo. We suggest that Got1p normally facilitates Sed5p-dependent fusion events, while Sft2p performs a related function in the late Golgi.
Conchon
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MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
Cao
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Barlowe
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Pelham
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HR
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D011992:Endosomes / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D005800:Genes, Fungal / Q000235:genetics / Q000502:physiology; D005804:Genes, Lethal / Q000235:genetics; D005816:Genetic Complementation Test; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D050765:Qa-SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; C120845:Got1 protein, S cerevisiae; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C077554:Sed5 protein, S cerevisiae; C120846:Sft2 protein, S cerevisiae; D033921:Vesicular Transport Proteins