Isolation of the structural proteins of western equine encephalitis virus by isoelectric focusing

Abstract

Western equine encephalitis virus was disrupted with Triton X-100 and subjected to isoelectric focusing in a sucrose or urea gradient. The two envelope proteins, E 1 and E 2 were not well separated in a sucrose gradient, while the E 1 and E 2 proteins were distinguished as two major peaks which focused in a urea gradient at about pH 7.5 and 10, respectively. Isolated E 1 protein refocused at pH 6.5 in a sucrose gradient isoelectric focusing column. When Western equine encephalitis virus was treated with Triton X-100 in 0.01 M phosphate buffer (pH 6), hemagglutinating E 1 protein was solubilized, which isoelectrofocused at pH 6.5. Purified nucleocapsids focused at pH 4 in a sucrose gradient on an isoelectric focusing column. After ribonuclease treatment of the purified nucleocapsid more than 95 per cent of the viral RNA was acid-soluble, and the nucleocapsid protein isoelectrofocused at about pH 4.