Glycosylation and stability of mature HIV envelope glycoprotein conformation under various conditions

Abstract

The role of the glycans of the mature human immunodeficiency virus (HIV) envelope (gp160) in its stability in various conditions was studied. gp160 conformation was monitored through its subsequent ability to bind ( 125I]CD4. Treatment of glycosylated (CHO+) gp160 with (i) sodium dodecyl sulfate (SDS) concentrations above 0.01% impaired subsequent CD4 binding while 0.3% SDS abolished it; (ii) β-mercaptoethanol (MSH) concentrations above 0.01% impaired CD4 binding while 0.03% MSH abolished it; (iii) 2 M guanidine-HCI had no effect; (iv) temperatures between 50C and 80C altered CD4 binding while, above 80C, the binding was abolished; (v) CD4 binding was decreased by 50% by 2 freeze-thaw cycles but was not further affected by subsequent (up to 15) cycles; (vi) gp160 incubation in serum or cell lysate had no effect on CD4 binding. Glycanase treated (CHO-) gp160 binding activity was only 3-fold lower than that of CHO+ gp160. Only 2 M guanidine-HCI and heating at 70C differentially affected the binding of CHO+ and CHOgp160, the effects being larger for CHO-gp160. CHO-gp160 binding was impaired after incubation in either serum or cell lysate. Thus, glycans stabilize gp160 conformation in some environments. However, CHO-gp160 appears to be resistant to denaturation as compared to other glycoproteins reported in the literature.