Fractionation of proteins from Rous sarcoma virus and avian myeloblastosis virus by isoelectric focusing.

The isoelectric focusing technique in the pH gradients was used for a preparative isolation of proteins from Rous sarcoma virus and avian myeloblastosis virus. The purified major gs protein, p27 (pI = 9.1) and the gP86 (pI = 5.3) were obtained after disruption of virus with 1% non-ionogenic detergent in the presence of 6M urea. The p10, p15, and p19 were present in the same range of pH (pI = 6.8). A strongly basic protein, immunologically active, presumably the p12, was found in the alkaline region of the pH gradient 10.8. These proteins fully retained their immunological activity. On the other hand, in the acidic region of the pH gradient between pH 4 and 5, strong precipitates were regularly found. These precipitates were complexes which were formed by interaction of the acid components of ampholines with the viral proteins during isoelectric focusing. Almost all viral proteins were present, differing only in quantity. The complexes were stabile in 1% non-inogenic detergent and 6M urea. They were dissociated with 1% SDS and 5M urea, and had no immunological activity. The methods of virus disruption and possibilities of formation of the ampholine-viral protein complexes are discussed.