Presence of a novel spleen focus-forming virus-specific glycoprotein (gp51) in a Friend leukemia cell line and its...

All Friend leukemia cell lines induced by polycythemic strains of Friend leukemia virus complex express an appreciable amount of spleen focus-forming virus (SFFV)-coding envelope gene (env)-related glycoprotein with a molecular weight of 55 kilodaltons (gp55). A clonal, highly differentiation-inducible Friend leukemia cell line, T3-C1-2-O(2-O), possesses not only gp55 but also gp51 as SFFV-specific gene products. The peptide map of gp51 is quite similar to that of gp55 and the difference in their molecular weights is primarily dependent on their oligosaccharide content. In the differentiation-induced state, gp51 becomes far less detectable than gp55 in 2-O cells. The biological significance of this novel SFFV-coding glycoprotein is discussed.