title: Yeast beta- and beta'-coat proteins (COP). Two coatomer subunits essential for endoplasmic reticulum-to-Golgi protein traffic.
abstract: To understand better the role of non-clathrin coat proteins in membrane traffic, we have cloned and characterized two essential genes encoding subunits of the yeast coatomer, SEC26 and SEC27. Sec26p is a 109-kDa protein that shares 43% sequence identity with mammalian beta-coat protein (beta-COP). Sec26p-depleted cells accumulate endoplasmic reticulum (ER) forms of secretory precursor proteins, and growth ceases after a dramatic accumulation of ER membranes. Sec26p overproduction partially suppresses sec27-1, a new mutant that shows a temperature-sensitive defect in ER-to-Golgi transport. The SEC27 gene was cloned, and the sequence predicts a 99.4-kDa protein with 45% sequence identity to mammalian beta'-COP. Our sequence data support a two-domain model for the SEC27 protein: a conserved amino-terminal domain, composed of five WD-40 repeats similar to those found in beta-subunits of trimeric G proteins, and a less conserved carboxyl-terminal domain. Genetic interactions connect sec27-1 and sec21-1 (coatomer gamma subunit) with the ARF1 and ARF2 genes and with the SEC22, BET1, and BOS1 genes, which encode membrane proteins involved in ER-to-Golgi transport.
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley 94720.
authors.forename: R
authors.initials: R
authors.lastname: Duden
authors.forename: M
authors.initials: M
authors.lastname: Hosobuchi
authors.forename: S
authors.initials: S
authors.lastname: Hamamoto
authors.forename: M
authors.initials: M
authors.lastname: Winey
authors.forename: B
authors.initials: B
authors.lastname: Byers
authors.forename: R
authors.initials: R
authors.lastname: Schekman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000235:genetics; D003001:Cloning, Molecular; D020756:Coatomer Protein; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D020756:Coatomer Protein; D005656:Fungal Proteins; D008565:Membrane Proteins