Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8648293 | Journal of Structural Biology | 2017 | 11 Pages |
Abstract
The structures of the compact and swollen southern bean mosaic virus (SBMV) particles have been compared by X-ray diffraction and proton magnetic resonance (PMR). Small-angle X-ray scattering showed that removal of divalent cations at alkaline pH causes the particle diameter to increase from 289Â Ã
in the native SBMV by 12% in solution and by 9% in microcrystals. The swelling is fully reversible upon re-addition of Ca2+ and Mg2+ ions, as shown by the X-ray patterns at 6Â Ã
resolution and by the 270Â MHz PMR spectra. Beyond 30Â Ã
resolution, X-ray patterns from the compact SBMV in solution and in microcrystals show fine fringes of â¼1/225Â Ã
â1 width extending to 6Â Ã
resolution, whereas patterns from the swollen SBMV in solution and in microcrystals show only broader fringes of â¼1/90Â Ã
â1 width, Model calculations demonstrate that the fine fringes from compact SBMV arise from regular packing of the protein subunits on the icosahedral surface lattice; the smearing of fine fringes in the swollen virus pattern can be simulated by uncorrelated displacements of pentamers and hexamers of protein subunits, with a standard deviation of 6Â Ã
from their mean locations. The PMR spectrum of compact SBMV is poorly resolved, whereas PMR spectrum of swollen SBMV shows sharp resonances in the methyl proton region. The line-narrowing for a fraction of the aliphatic protons upon swelling cannot be accounted for by rotational relaxation of the particle of 6Â ÃÂ 106Â MW, but must be attributed to internal motion in small regions of the protein subunits.
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Molecular Biology
Authors
Jade Li, Carl Fricks, Ivan Rayment, Donald L.D. Caspar,