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. This endogenous envelope protein has lost its original fusogenic properties. SU mediates receptor recognition. TM anchors the envelope heterodimer to the viral membrane through one transmembrane domain. The other hydrophobic domain, called fusion peptide, mediates fusion of the viral membrane with the target cell membrane (By similarity). The surface (SU) and transmembrane (TM) proteins form a heterodimer. SU and TM are attached by noncovalent interactions or by a labile interchain disulfide bond (By similarity). Low expression in testis. Specific enzymatic cleavages in vivo yield the mature SU and TM proteins. Orthologs in P.troglodytes, G.gorilla (truncated) and P.pygmaeus (truncated). HERV-H family subgenomic RNAs have been observed. This provirus is intergenic, the closest flanking genes being KCNJ3 and NR4A2. Belongs to the gamma type-C retroviral envelope protein family. HERV class-I H env subfamily. Lacks the CX6CC and the CKS-17 domains.