title: COPII subunit interactions in the assembly of the vesicle coat.
abstract: In vitro analysis of COPII vesicle formation in the yeast Saccharomyces cerevisiae has demonstrated the requirement for three cytosolic factors: Sec31p-Sec13p, Sec23p-Sec24p, and Sar1p. Convergent evidence suggests that the peripheral endoplasmic reticulum (ER) membrane protein Sec16p also represents an important component of the vesicle assembly apparatus: SEC16 interacts genetically with all five COPII genes; Sec16p binds to Sec23p and Sec24p, is found on ER-derived transport vesicles, and is required in vitro for the efficient release of ER-derived vesicle cargo. In this report, we demonstrate an important functional interaction between Sec16p and Sec31p. First, we map onto Sec31p binding regions for Sec16p, Sec23p, Sec24p, and Sec13p. Second, we show that a truncation mutant of Sec31p specifically defective for Sec16p binding is unable to complement a sec31Delta mutant and cannot rescue the secretion defect of a temperature-sensitive sec31 mutant at nonpermissive temperatures. We propose that Sec16p organizes the assembly of a coat that is stabilized both by the interaction of Sec31p with Sec23p and Sec24p and by the interaction of these three components with Sec16p.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Shaywitz
authors.forename: P J
authors.initials: PJ
authors.lastname: Espenshade
authors.forename: R E
authors.initials: RE
authors.lastname: Gimeno
authors.forename: C A
authors.initials: CA
authors.lastname: Kaiser
mesh_terms: D001665:Binding Sites; D022181:COP-Coated Vesicles; D002352:Carrier Proteins / Q000378:metabolism*; D018699:Coated Vesicles / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006056:Golgi Apparatus / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D020559:Monomeric GTP-Binding Proteins; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins; C079620:SEC13 protein, S cerevisiae; C096367:SEC16 protein, S cerevisiae; C079037:SEC23 protein, S cerevisiae; C106113:SEC31 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins; C077395:SAR1 protein, S cerevisiae