title: The yeast orthologue of GRASP65 forms a complex with a coiled-coil protein that contributes to ER to Golgi traffic.
abstract: The mammalian Golgi protein GRASP65 is required in assays that reconstitute cisternal stacking and vesicle tethering. Attached to membranes by an N-terminal myristoyl group, it recruits the coiled-coil protein GM130. The relevance of this system to budding yeasts has been unclear, as they lack an obvious orthologue of GM130, and their only GRASP65 relative (Grh1) lacks a myristoylation site and has even been suggested to act in a mitotic checkpoint. In this study, we show that Grh1 has an N-terminal amphipathic helix that is N-terminally acetylated and mediates association with the cis-Golgi. We find that Grh1 forms a complex with a previously uncharacterized coiled-coil protein, Ydl099w (Bug1). In addition, Grh1 interacts with the Sec23/24 component of the COPII coat. Neither Grh1 nor Bug1 are essential for growth, but biochemical assays and genetic interactions with known mediators of vesicle tethering (Uso1 and Ypt1) suggest that the Grh1-Bug1 complex contributes to a redundant network of interactions that mediates consumption of COPII vesicles and formation of the cis-Golgi.
authors.affiliation: Laboratory of Molecular Biology, Medical Research Council, Cambridge CB2 2QH, England, UK.
authors.forename: Rudy
authors.initials: R
authors.lastname: Behnia
authors.forename: Francis A
authors.initials: FA
authors.lastname: Barr
authors.forename: John J
authors.initials: JJ
authors.lastname: Flanagan
authors.forename: Charles
authors.initials: C
authors.lastname: Barlowe
authors.forename: Sean
authors.initials: S
authors.lastname: Munro
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018699:Coated Vesicles / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D017353:Gene Deletion; D006056:Golgi Apparatus / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C108705:GORASP1 protein, human; C519806:GRASP65 protein, S cerevisiae; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; C106113:SEC31 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins