title: 3.3 A cryo-EM structure of a nonenveloped virus reveals a priming mechanism for cell entry.
abstract: To achieve cell entry, many nonenveloped viruses must transform from a dormant to a primed state. In contrast to the membrane fusion mechanism of enveloped viruses (e.g., influenza virus), this membrane penetration mechanism is poorly understood. Here, using single-particle cryo-electron microscopy, we report a 3.3 A structure of the primed, infectious subvirion particle of aquareovirus. The density map reveals side-chain densities of all types of amino acids (except glycine), enabling construction of a full-atom model of the viral particle. Our structure and biochemical results show that priming involves autocleavage of the membrane penetration protein and suggest that Lys84 and Glu76 may facilitate this autocleavage in a nucleophilic attack. We observe a myristoyl group, covalently linked to the N terminus of the penetration protein and embedded in a hydrophobic pocket. These results suggest a well-orchestrated process of nonenveloped virus entry involving autocleavage of the penetration protein prior to exposure of its membrane-insertion finger.
authors.affiliation: Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095-7364, USA.
authors.forename: Xing
authors.initials: X
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Jin
authors.forename: Qin
authors.initials: Q
authors.lastname: Fang
authors.forename: Wong H
authors.initials: WH
authors.lastname: Hui
authors.forename: Z Hong
authors.initials: ZH
authors.lastname: Zhou
mesh_terms: D036022:Capsid Proteins / Q000378:metabolism; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D012087:Reoviridae / Q000378:metabolism* / Q000648:ultrastructure*; D013696:Temperature; D053586:Virus Internalization
chemical_list: D036022:Capsid Proteins
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