Carbon-13 NMR study of southern bean mosaic virus

The motional state of the coat protein of southern bean mosaic virus (SBMV) particles has been studied by 13C NMR at 50.3 MHz. In the native virus, 13C-NMR signals are observed only from a few highly mobile amino acid side chain groups such as methyls or from unprotonated carbons such as carbonyls or arginine-zeta. After swelling SBMV by treating with EDTA, additional 13C-NMR peaks become visible. The pattern of resonances matches that expected from the side chains of those amino acid residues identified to be on the surface of the virus particle based on the known crystal structure. After further disruption of the virus structure by 0.5 M KCl, the 13C-NMR peaks sharpen, and additional peaks appear, but the set of peaks appears to correspond only to surface amino acid side chains.