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A mechanism by which binding of the broadly neutralizing antibody b12 unfolds the inner domain α1 helix in an engineered HIV-1 gp120
Journal article   Open access   Peer reviewed

A mechanism by which binding of the broadly neutralizing antibody b12 unfolds the inner domain α1 helix in an engineered HIV-1 gp120

Ali Emileh and Cameron F Abrams
Proteins, structure, function, and bioinformatics, v 79(2), pp 537-546
Feb 2011
PMID: 21117239
url
https://doi.org/10.1002/prot.22901View
Published, Version of Record (VoR) Open

Abstract

HIV Envelope Protein gp120 - genetics Protein Structure, Tertiary Protein Structure, Secondary Protein Unfolding Humans HIV Antibodies - chemistry HIV Envelope Protein gp120 - metabolism Molecular Dynamics Simulation HIV-1 - immunology Antibodies, Neutralizing - chemistry Protein Binding Protein Interaction Domains and Motifs HIV Envelope Protein gp120 - chemistry Mutation Binding Sites, Antibody
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 α1-helix upon binding of b12. Using targeted molecular dynamics, we show that folded α1 in the b12-bound conformation of gp120 is stable both with and without the stitch, but that with folded α1, the stitch requires an orientation of the β20/β21 sheet that is sterically incompatible with b12 binding. Forcing β20/β21 into the orientation displayed by the b12-bound conformation after folding α1 with the stitch intact results in partial unfolding of α1, whereas without the stitch, β20/β21 reorientation does not affect the conformation of α1. These findings collectively support the hypothesis that the disulfide stitch shifts the conformational distribution of α1 to the unfolded state, meaning an unfolded α1 is not a strict requirement of the b12-bound conformational ensemble of gp120's lacking the I109C/Q428C stitch.

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Web of Science research areas
Biochemistry & Molecular Biology
Biophysics
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