Reversible swelling of sbmv is associated with reversible disordering.

Reversible swelling of sbmv is associated with reversible disordering.
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Li J, Fricks C, Caspar DLD, Rayment I,


Li J, Fricks C, Caspar DLD, Rayment I, (click to view)

Li J, Fricks C, Caspar DLD, Rayment I,

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Journal of structural biology 2017 06 21() pii S1047-8477(17)30106-5
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 289Å in the native SBMV by 12% in solution and by 9% in microcrystals. The swelling is fully reversible upon re-addition of Ca(2+)and Mg(2+) ions, as shown by the X-ray patterns at 6 Å resolution and by the 270 MHz PMR spectra. Beyond 30Å resolution, X-ray patterns from the compact SBMV in solution and in microcrystals show fine fringes of ∼1/225 Å(-1) width extending to 6 Å resolution, whereas patterns from the swollen SBMV in solution and in microcrystals show only broader fringes of ∼1/90 Å(-1) 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 6 Å 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 6×10(6) MW, but must be attributed to internal motion in small regions of the protein subunits.

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