title: Multiple cargo binding sites on the COPII subunit Sec24p ensure capture of diverse membrane proteins into transport vesicles.
abstract: We have characterized the mechanisms of cargo selection into ER-derived vesicles by the COPII subunit Sec24p. We identified a site on Sec24p that recognizes the v-SNARE Bet1p and show that packaging of a number of cargo molecules is disrupted when mutations are introduced at this site. Surprisingly, cargo proteins affected by these mutations did not share a single common sorting signal, nor were proteins sharing a putative class of signal affected to the same degree. We show that the same site is conserved as a cargo-interaction domain on the Sec24p homolog Lst1p, which only packages a subset of the cargoes recognized by Sec24p. Finally, we identified an additional mutation that defines another cargo binding domain on Sec24p, which specifically interacts with the SNARE Sec22p. Together, our data support a model whereby Sec24p proteins contain multiple independent cargo binding domains that allow for recognition of a diverse set of sorting signals.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Miller
authors.forename: Traude H
authors.initials: TH
authors.lastname: Beilharz
authors.forename: Per N
authors.initials: PN
authors.lastname: Malkus
authors.forename: Marcus C S
authors.initials: MC
authors.lastname: Lee
authors.forename: Susan
authors.initials: S
authors.lastname: Hamamoto
authors.forename: Lelio
authors.initials: L
authors.lastname: Orci
authors.forename: Randy
authors.initials: R
authors.lastname: Schekman
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D022181:COP-Coated Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021382:Protein Sorting Signals; D020836:Protein Structure, Quaternary; D021381:Protein Transport / Q000502:physiology; D050767:Qc-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D033921:Vesicular Transport Proteins
chemical_list: C107845:BET1 protein, S cerevisiae; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D021382:Protein Sorting Signals; D050767:Qc-SNARE Proteins; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; C106113:SEC31 protein, S cerevisiae; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C444081:Sys1 protein, S cerevisiae; D033921:Vesicular Transport Proteins