4l3b
From Proteopedia
X-ray structure of the HRV2 A particle uncoating intermediate
Structural highlights
Function[POLG_HRV2] Capsid proteins VP1, VP2, VP3 and VP4 form a closed capsid enclosing the viral positive strand RNA genome. VP4 lies on the inner surface of the protein shell formed by VP1, VP2 and VP3. All the three latter proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The capsid interacts with human VLDLR to provide virion attachment to target cell. This attachment induces virion internalization predominantly through clathrin-mediated endocytosis. VP4 and VP1 subsequently undergo conformational changes leading to the formation of a pore in the endosomal membrane, thereby delivering the viral genome into the cytoplasm.[1] [2] VP0 precursor is a component of immature procapsids (By similarity).[3] [4] Protein 2A is a cysteine protease that is responsible for the cleavage between the P1 and P2 regions. It cleaves the host translation initiation factor EIF4G1, in order to shut down the capped cellular mRNA transcription.[5] [6] Protein 2B affects membrane integrity and cause an increase in membrane permeability (By similarity).[7] [8] Protein 2C associates with and induces structural rearrangements of intracellular membranes. It displays RNA-binding, nucleotide binding and NTPase activities (By similarity).[9] [10] Protein 3A, via its hydrophobic domain, serves as membrane anchor (By similarity).[11] [12] Protein 3C is a cysteine protease that generates mature viral proteins from the precursor polyprotein. In addition to its proteolytic activity, it binds to viral RNA, and thus influences viral genome replication. RNA and substrate bind co-operatively to the protease (By similarity).[13] [14] RNA-directed RNA polymerase 3D-POL replicates genomic and antigenomic RNA by recognizing replications specific signals (By similarity).[15] [16] Publication Abstract from PubMedDuring infection, viruses undergo conformational changes that lead to delivery of their genome into host cytosol. In human rhinovirus A2, this conversion is triggered by exposure to acid pH in the endosome. The first subviral intermediate, the A-particle, is expanded and has lost the internal viral protein 4 (VP4), but retains its RNA genome. The nucleic acid is subsequently released, presumably through one of the large pores that open at the icosahedral twofold axes, and is transferred along a conduit in the endosomal membrane; the remaining empty capsids, termed B-particles, are shuttled to lysosomes for degradation. Previous structural analyses revealed important differences between the native protein shell and the empty capsid. Nonetheless, little is known of A-particle architecture or conformation of the RNA core. Using 3D cryo-electron microscopy and X-ray crystallography, we found notable changes in RNA-protein contacts during conversion of native virus into the A-particle uncoating intermediate. In the native virion, we confirmed interaction of nucleotide(s) with Trp(38) of VP2 and identified additional contacts with the VP1 N terminus. Study of A-particle structure showed that the VP2 contact is maintained, that VP1 interactions are lost after exit of the VP1 N-terminal extension, and that the RNA also interacts with residues of the VP3 N terminus at the fivefold axis. These associations lead to formation of a well-ordered RNA layer beneath the protein shell, suggesting that these interactions guide ordered RNA egress. Uncoating of common cold virus is preceded by RNA switching as determined by X-ray and cryo-EM analyses of the subviral A-particle.,Pickl-Herk A, Luque D, Vives-Adrian L, Querol-Audi J, Garriga D, Trus BL, Verdaguer N, Blaas D, Caston JR Proc Natl Acad Sci U S A. 2013 Dec 10;110(50):20063-8. doi:, 10.1073/pnas.1312128110. Epub 2013 Nov 25. PMID:24277846[17] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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