Betaretroviral Envelope Subunits Are Noncovalently Associated and Restricted to the Mammalian Class

摘要: The structure of the transmembrane subunit (TM) retroviral envelope glycoprotein (Env) is highly conserved among most retrovirus genera and includes a pair cysteines that forms an intramolecular disulfide loop within ectodomain. Alpha-, gamma-, deltaretroviruses have third cysteine, adjacent to loop, which bond between TM surface (SU) Env, while lentiviruses, noncovalently associated subunits, lack this cysteine. Betaretrovirus genus Jaagsiekte sheep (JSRV) mouse mammary tumor virus (MMTV), as well many endogenous retroviruses. Envelope association had not been characterized in betaretroviruses, but cysteine ectodomain suggested subunits. We tested Env proteins JSRV MMTV, human K (HERV-K)108—a betaretrovirus-like retrovirus—for intersubunit bonding found that, subunits bond. Since these results suggest number region readily distinguishes covalent noncovalent structure, we surveyed sequences genomes vertebrates represented public databases (i) retroviruses with present during all anthropoid evolution (ii) env motif limited mammals, type five vertebrate classes. discuss implications findings for evolution, cross-species transmissions, recombination events involving gene.