Very broad distribution of β sheet registries of the HIV gp41 fusion peptide supports mutational robustness for fusion and infection

• 成果类型: Article
• 署名作者: Zhang, Yijin; Schmick, Scott D.; Xie, Li; Ghosh, Ujjayini; Weliky, David P.
• 署名单位: Wuhan University of Science & Technology; 3M; St Jude Children's Research Hospital; Michigan State University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12284
• DOI: 10.1073/pnas.2402953121
• 发表日期: 2024-12-10
• 关键词: solid-state nmr; nuclear-magnetic-resonance; membrane-fusion; transmembrane protein; extended conformation; strand conformation; rotational-echo; antiparallel; ectodomain; locations

摘要

HIV, like other membrane-enveloped viruses, has protein spikes that include a fusion peptide (Fp) segment that binds the host cell membrane and plays a critical role in fusion (joining) viral and cell membranes. The HIV Fp is the similar to 23 N-terminal residues of the gp41 spike protein. Fp adopts intermolecular antiparallel beta sheet structure when lipid fraction cholesterol approximate to 0.3, which is comparable to host cells. Rotational-echo double-resonance NMR was applied to probe the registries (alignments) of adjacent Fp molecules in membrane-bound sheets. The data were fitted to determine quantitative populations, f(t)'s, of individual antiparallel registries indexed by t, the number of residues in the registry. Both wild-type (WT) and fusion-defective V2E Fp sheets have broad but very different registry distributions, each with at least eight populated registries with f(t) > 0.02, and < t >(WT)=16.1 and < t >(V2E) = 18.5. The broad WT distribution likely improves mutational robustness for HIV, as Fp is a neutralization epitope of the immune system, and Fp mutations are required for immune evasion during chronic HIV infection. V2E fusion is reduced because longer Fp sheets increase separation between initially apposed membranes. The f(t)(WT) were well-fitted to free energies that were sums of contributions from sheet length, aligned leucines, and sidechain membrane insertion. The f(t)(V2E)'s were similarly well-fitted except there wasn't the insertion contribution. Relative to V2E, WT fusion is enhanced by deeper membrane insertion of Fp with accompanying greater dislocation of neighboring lipids. This study provides a rare quantitative determination of broad molecular structural distributions by experiment.