title: A pseudoatomic model of the COPII cage obtained from cryo-electron microscopy and mass spectrometry.
abstract: COPII vesicles transport proteins from the endoplasmic reticulum to the Golgi apparatus. Previous COPII-cage cryo-EM structures lacked the resolution necessary to determine the residues of Sec13 and Sec31 that mediate assembly and flexibility of the COPII cage. Here we present a 12-Å structure of the human COPII cage, where the tertiary structure of Sec13 and Sec31 is clearly identifiable. We employ this structure and a homology model of the Sec13-Sec31 complex to create a reliable pseudoatomic model of the COPII cage. We combined this model with hydrogen/deuterium-exchange MS analysis to characterize four distinct contact regions at the vertices of the COPII cage. Furthermore, we found that the two-fold symmetry of the Sec31 dimeric region in Sec13-Sec31 is broken upon cage formation and that the resulting hinge is essential to form the proper edge geometry in COPII cages.
authors.affiliation: Department of Physics, Florida State University, Tallahassee, Florida, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Noble
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
authors.forename: Jason
authors.initials: J
authors.lastname: O'Donnell
authors.forename: Hanaa
authors.initials: H
authors.lastname: Hariri
authors.forename: Nilakshee
authors.initials: N
authors.lastname: Bhattacharya
authors.forename: Alan G
authors.initials: AG
authors.lastname: Marshall
authors.forename: Scott M
authors.initials: SM
authors.lastname: Stagg
mesh_terms: D001483:Base Sequence; D022181:COP-Coated Vesicles / Q000737:chemistry* / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D020285:Cryoelectron Microscopy / Q000379:methods; D041961:Deuterium Exchange Measurement; D006801:Humans; D007091:Image Processing, Computer-Assisted; D013058:Mass Spectrometry / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics; D015003:Yeasts
chemical_list: D002352:Carrier Proteins; C507456:SEC13 protein, human; C507455:SEC31A protein, human; D033921:Vesicular Transport Proteins