title: Membrane rupture generates single open membrane sheets during vaccinia virus assembly.
abstract: The biogenesis and dynamics of cellular membranes are governed by fusion and fission processes that ensure the maintenance of closed compartments. These principles also apply to viruses during acquisition of their envelope. Based on conventional electron microscopy (EM), however, it has been proposed that poxviruses assemble from membranes made de novo with "free" ends in the cytoplasm. Here, we analyze the origin and structure of poxvirus membranes in a close-to-native state and in three dimensions by using cryopreservation and electron tomography (ET). By cryo-EM, the precursor membrane of poxviruses appears as an open membrane sheet stabilized by a protein scaffold. ET shows that this membrane is derived from pre-existing cellular membranes that rupture to generate an open compartment, rather than being made de novo. Thus, poxvirus infection represents an excellent system to study how cytoplasmic membranes can form open sheets by a process distinct from well-defined mechanisms of membrane biogenesis.
authors.affiliation: Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany. chlanda@embl.de
authors.forename: Petr
authors.initials: P
authors.lastname: Chlanda
authors.forename: Maria Alejandra
authors.initials: MA
authors.lastname: Carbajal
authors.forename: Marek
authors.initials: M
authors.lastname: Cyrklaff
authors.forename: Gareth
authors.initials: G
authors.lastname: Griffiths
authors.forename: Jacomine
authors.initials: J
authors.lastname: Krijnse-Locker
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D020285:Cryoelectron Microscopy / Q000379:methods; D055032:Electron Microscope Tomography / Q000379:methods; D014616:Vaccinia virus / Q000502:physiology*; D014771:Virion / Q000648:ultrastructure*; D019065:Virus Assembly