This family comes from human endogenous retrovirus K envelope glycoproteins.

1: Survey of human genes of retroviral origin: identification and transcriptome of the genes with coding capacity for complete envelope proteins. de Parseval N, Lazar V, Casella JF, Benit L, Heidmann T; J Virol. 2003;77:10414-10422. PMID:12970426