Retroviral envelope proteins mediate receptor recognition and membrane fusion during early infection. Endogenous envelope proteins may have kept, lost or modified their original function during evolution. At the origin, this retroviral envelope protein was localized in the virion. The CKS-17 immunosuppressive domain is present in many retroviral envelope proteins. As a synthetic peptide, it inhibits immune function in vitro and in vivo (By similarity). Specific enzymatic cleavages in vivo yield the mature SU and TM proteins. The CXXC motif is highly conserved across a broad range of retroviral envelope proteins. It is thought to participate in the formation of a labile disulfide bond possibly with the CX6CC motif present in the transmembrane domain (By similarity). This envelope protein is encoded by a baboon specific provirus. It has no ortholog in human. Belongs to the gamma type-C retroviral envelope protein family. HERV class-I F(c)1 env subfamily. The cleavage site does not match the consensus.