Authors: Julien Roche John M Louis Annie Aniana Rodolfo Ghirlando Ad Bax
Publish Date: 2015/01/29
Volume: 61, Issue: 3-4, Pages: 235-248
Abstract
The envelope glycoprotein gp41 mediates the process of membrane fusion that enables entry of the HIV1 virus into the host cell Strong lipid affinity of the ectodomain suggests that its heptad repeat regions play an active role in destabilizing membranes by directly binding to the lipid bilayers and thereby lowering the freeenergy barrier for membrane fusion In such a model immediately following the shedding of gp120 the Nheptad and Cheptad helices dissociate and melt into the host cell and viral membranes respectively pulling the destabilized membranes into juxtaposition ready for fusion Postfusion reaching the final 6helix bundle 6HB conformation then involves competition between intermolecular interactions needed for formation of the symmetric 6HB trimer and the membrane affinity of gp41’s ectodomain including its membraneproximal regions Our solution NMR study of the structural and dynamic properties of three constructs containing the ectodomain of gp41 with and without its membraneproximal regions suggests that these segments do not form interhelical interactions until the very late steps of the fusion process Interactions between the polar termini of the heptad regions which are not associating with the lipid surface therefore may constitute the main driving force initiating formation of the final postfusion states The absence of significant intermolecular ectodomain interactions in the presence of dodecyl phosphocholine highlights the importance of trimerization of gp41’s transmembrane helix to prevent complete dissociation of the trimer during the course of fusionWe thank Drs James Baber and Jinfa Ying for technical support and acknowledge support from the Advanced Mass Spectrometry Core of the National Institute of Diabetes and Digestive and Kidney Diseases NIDDK This work was funded by the NIH Intramural Research Program of the NIDDK and by the Intramural AIDSTargeted Antiviral Program of the Office of the Director NIH
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