title: Membrane proteins organize a symmetrical virus.
abstract: Alphaviruses are enveloped icosahedral viruses that mature by budding at the plasma membrane. According to a prevailing model maturation is driven by binding of membrane protein spikes to a preformed nucleocapsid (NC). The T = 4 geometry of the membrane is thought to be imposed by the NC through one-to-one interactions between spike protomers and capsid proteins (CPs). This model is challenged here by a Semliki Forest virus capsid gene mutant. Its CPs cannot assemble into NCs, or its intermediate structures, due to defective CP-CP interactions. Nevertheless, it can use its horizontal spike-spike interactions on membrane surface and vertical spike-CP interactions to make a particle with correct geometry and protein stoichiometry. Thus, our results highlight the direct role of membrane proteins in organizing the icosahedral conformation of alphaviruses.
authors.affiliation: Karolinska Institute, Department of Biosciences at Novum, S-141 57 Huddinge, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Forsell
authors.forename: L
authors.initials: L
authors.lastname: Xing
authors.forename: T
authors.initials: T
authors.lastname: Kozlovska
authors.forename: R H
authors.initials: RH
authors.lastname: Cheng
authors.forename: H
authors.initials: H
authors.lastname: Garoff
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D019251:Nucleocapsid / Q000378:metabolism; D019590:Nucleocapsid Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012672:Semliki forest virus / Q000378:metabolism / Q000502:physiology*; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014771:Virion / Q000378:metabolism*; D019065:Virus Assembly
chemical_list: D008562:Membrane Glycoproteins; D019590:Nucleocapsid Proteins; D014759:Viral Envelope Proteins