title: Placement of the structural proteins in Sindbis virus.
abstract: The structure of the lipid-enveloped Sindbis virus has been determined by fitting atomic resolution crystallographic structures of component proteins into an 11-A resolution cryoelectron microscopy map. The virus has T=4 quasisymmetry elements that are accurately maintained between the external glycoproteins, the transmembrane helical region, and the internal nucleocapsid core. The crystal structure of the E1 glycoprotein was fitted into the cryoelectron microscopy density, in part by using the known carbohydrate positions as restraints. A difference map showed that the E2 glycoprotein was shaped similarly to E1, suggesting a possible common evolutionary origin for these two glycoproteins. The structure shows that the E2 glycoprotein would have to move away from the center of the trimeric spike in order to expose enough viral membrane surface to permit fusion with the cellular membrane during the initial stages of host infection. The well-resolved E1-E2 transmembrane regions form alpha-helical coiled coils that were consistent with T=4 symmetry. The known structure of the capsid protein was fitted into the density corresponding to the nucleocapsid, revising the structure published earlier.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Suchetana
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Pletnev
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Baker
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Kuhn
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rossmann
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins; D020285:Cryoelectron Microscopy; D008562:Membrane Glycoproteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000737:chemistry; D012845:Sindbis Virus / Q000737:chemistry*; D014759:Viral Envelope Proteins / Q000737:chemistry; D015678:Viral Structural Proteins / Q000737:chemistry*
chemical_list: D036022:Capsid Proteins; D008562:Membrane Glycoproteins; D012367:RNA, Viral; D014759:Viral Envelope Proteins; D015678:Viral Structural Proteins; C022012:glycoprotein E1, Sindbis virus; C064950:glycoprotein E2, Sindbis virus