A mechanism by which binding of the broadly neutralizing antibody b12 unfolds the inner domain ?1 helix in an engineered HIV-1 gp120.
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ABSTRACT: Using all-atom simulations, we examine the role of the I109C/Q428C disulfide "stitch" in altering the conformational distribution of engineered HIV-1 gp120 core relevant for binding of the broadly neutralizing recombinant antibody b12. In particular, we propose that the I109C/Q428C stitch results in a conformational distribution favoring an unfolded inner-domain ?1-helix upon binding of b12. Using targeted molecular dynamics, we show that folded ?1 in the b12-bound conformation of gp120 is stable both with and without the stitch, but that with folded ?1, the stitch requires an orientation of the ?20/?21 sheet that is sterically incompatible with b12 binding. Forcing ?20/?21 into the orientation displayed by the b12-bound conformation after folding ?1 with the stitch intact results in partial unfolding of ?1, whereas without the stitch, ?20/?21 reorientation does not affect the conformation of ?1. These findings collectively support the hypothesis that the disulfide stitch shifts the conformational distribution of ?1 to the unfolded state, meaning an unfolded ?1 is not a strict requirement of the b12-bound conformational ensemble of gp120's lacking the I109C/Q428C stitch.
SUBMITTER: Emileh A
PROVIDER: S-EPMC3059550 | biostudies-literature | 2011 Feb
REPOSITORIES: biostudies-literature
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