1ohf

File:1ohf.jpg

spinqualitylabelsall models 1ohf, resolution 2.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

THE REFINED STRUCTURE OF NUDAURELIA CAPENSIS OMEGA VIRUS

OverviewOverview

Large-scale reorganization of protein interactions characterizes many, biological processes, yet few systems are accessible to biophysical, studies that display this property. The capsid protein of Nudaurelia, capensis omega Virus (NomegaV) has previously been characterized in two, dramatically different T = 4 quasi-equivalent assembly states when, expressed as virus-like particles (VLPs) in a baculovirus system. The, procapsid (pH 7), is round, porous, and approximately 450 A in diameter., It converts, in vitro, to the capsid form at pH 5 and the capsid is sealed, shut, shaped like an icosahedron, has a maximum diameter of 410 A and, undergoes an autocatalytic cleavage at residue 570. Residues 571-644, the, gamma peptide, remain associated with the particle and are partially, ordered. The interconversion of these states has been previously studied, by solution X-ray scattering, electron cryo microscopy (CryoEM), and, site-directed mutagenesis. The particle structures appear equivalent in, authentic virions and the low pH form of the expressed and assembled, protein. Previously, and before the discovery of the multiple, morphological forms of the VLPs, we reported the X-ray structure of, authentic NomegaV at 2.8 A resolution. These coordinates defined the fold, of the protein but were not refined at the time because of technical, issues associated with the approximately 2.5 million reflection data set., We now report the refined, authentic virus structure that has added 29, residues to the original model and allows the description of the chemistry, of molecular switching for T = 4 capsid formation and the multiple, morphological forms. The amino and carboxy termini are internal, predominantly helical, and disordered to different degrees in the four, structurally independent subunits; however, the refined structure shows, significantly more ordered residues in this region, particularly at the, amino end of the B subunit that is now seen to invade space occupied by, the A subunits. These additional residues revealed a previously unnoticed, strong interaction between the pentameric, gamma peptide helices of the A, and B subunits that are largely proximal to the quasi-6-fold axes. One, C-terminal helix is ordered in the C and D subunits and stabilizes a flat, interaction in two interfaces between the protein monomers while the, other, quasi-equivalent, interactions are bent. As this helix is arginine, rich, the comparable, disordered region in the A and B subunits probably, interacts with RNA. One of the subunit-subunit interfaces has an unusual, arrangement of carboxylate side chains. Based on this observation, we, propose a mechanism for the control of the pH-dependent transitions of the, virus particle.

About this StructureAbout this Structure

1OHF is a Single protein structure of sequence from Nudaurelia capensis omega virus with as ligand. Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

The refined structure of Nudaurelia capensis omega virus reveals control elements for a T = 4 capsid maturation., Helgstrand C, Munshi S, Johnson JE, Liljas L, Virology. 2004 Jan 5;318(1):192-203. PMID:14972547

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