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[摘要]：The HIV gp41 protein catalyzes fusion between viral and host cell membranes, and its apolar N-terminal region or "fusion peptide" binds to the host cell membrane and plays a key role in fusion. "HFP" is a construct containing the fusion peptide sequence, induces membrane vesicle fusion, and is an important fusion model system. Earlier solid-state nuclear magnetic resonance (SSNMR) studies showed that when H FP is associated with membranes with similar to 30 mol % cholesterol, the first 16 residues have predominant beta strand secondary structure and a fraction of the strands form antiparallel beta sheet structure with residue 16 -> 1/1 -> 16 or 17 -> 1/1 -> 17 registries for adjacent strands. In some contrast, other SSNM R and infrared studies have been interpreted to support a large fraction of an approximately in-register parallel registry of adjacent strands. However, the samples had extensive isotopic labeling, and other structural models were also consistent with the data. This SSNM R study uses sparse labeling schemes that reduce ambiguity in the determination of the fraction of 11 FP molecules with parallel beta registry. Quantitative analysis of the data shows that the parallel fraction is at most 0.15 with a much greater fraction of antiparallel 16 -> 1/1 -> 16 and 17 -> 1/1 -> 17 registries. These data strongly support a model of HET-induced vesicle fusion caused by antiparallel rather than parallel registries and provide insight into the arrangement of gp41 molecules during HIV-host cell fusion. This study is an example of quantitative determination of a complex structural distribution by SSNMR, including experimentally validated inclusion of natural abundance contributions to the SSNM R data. |
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