Expression, purification, and characterization of recombinant HIV gp140 - The gp41 ectodomain of HIV or simian immunodeficiency virus is sufficient to maintain the retroviral envelope glycoprotein as a trimer

Efforts to understand the molecular basis of human immunodeficiency virus ( HM envelope glycoprotein function have been hampered by the inability to ge nerate sufficient quantities of homogeneous material. We now report on the high level expression, purification, and characterization of soluble HIV gp 140 ectodomain proteins in Chinese hamster ovary-Lec3.2.8.1 cells. Gel filt ration and analytical ultracentrifugation show that the uncleaved ADA strai n-derived gp140 proteins are trimeric without further modification required to maintain oligomers. These spike proteins are native as judged by solubl e CD4 (sCD4) (K-D = 1-2 nm) and monoclonal antibody binding studies using s urface plasmon resonance. CD4 ligation induces conformational change in the trimer, exposing the chemokine receptor binding site as assessed by 17b mo noclonal antibody reactivity. Lack of anti-cooperativity in sCD4-ADA trimer interaction distinct from that observed with sCD4-SrV mac32H implies quate rnary structural differences in ground states of their respective spike pro teins.