Family of a vain specific viral glycoproteins that forms a receptor-binding gp85 polypeptide that is linked through disulfide to a membrane-spanning gp37 spike. Gp85 confers a high degree of subgroup specificity for interaction with distinct cell receptors [1].

1: Determinants for receptor interaction and cell killing on the avian retrovirus glycoprotein gp85. Dorner AJ, Coffin JM; Cell 1986;45:365-374. PMID:3009025