Abstract
Summary SDS-polyacrylamide gel electrophoresis showed that purified sowthistle yellow vein virus (SYVV) contains four major and one minor structural polypeptides. The mol. wt. were estimated to be approx. 150000, 83000 (G), 60000 (N), 44000 (M1) and 36000 (M2). Covalently bound carbohydrate was detected in the 150000 mol. wt. species and the G protein. Saponin and Nonidet P40 treatment removed the projections and membrane; however, the resultant bullet-shaped nucleocapsid structures, which contained N protein, were unstable and readily uncoiled into strands. Trypsin and thermolysin treatment removed the surface projections, and the G protein and high mol. wt. protein. Enzymically liberated G protein had a mol. wt. 5000 to 7000 smaller than attached G protein, suggesting that a 5000 to 7000 mol. wt. part of the G protein was left embedded in the membrane. Lactoperoxidase- and chloramine T-catalysed iodination of intact SYVV particles labelled the G protein first, confirming its external location. The M1 and M2 proteins were the next labelled and were considered to be membrane associated. The N protein and the high mol. wt. protein were the last to be labelled.

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