Envelope glycoproteins of Rauscher murine leukemia virus: isolation and chemical characterization

Abstract

The envelope glycoproteins (designated gp70 and gp45) of the Rauscher strain of murine leukemia virus were solubilized by osmotic shock and freeze-thawing in chaotropic solutions. The viral glycoproteins were then purified by phosphocellulose chromatography and gel permeation chromatography on Bio-Gel A-1.5m. Yields by this procedure were 6.2% for gp70 and 1.3% for gp45 on a protein input basis. The apparent MW were 67,500 and 47,500, respectively, with a polypeptide chain MW of .apprx. 45,000 for both glycoproteins. Amino acid analysis showed a high degree of similarity for both components, with some differences subject to further evaluation. The total carbohydrate content was .apprx. 32% for gp70 and 6-9% for gp45. In keeping with the amino acid compositional similarity suggesting relationships, alanine was the amino-terminal amino acid of both glycoproteins, and cross-reactivity was demonstrated by immunologic tests. The chief difference between gp70 and gp45 probably lies in the carbohydrate content.