Changes in lipid bilayer structure caused by the helix-to-sheet transition of an HIV-1 gp41 fusion peptide derivative

• Published in: Chemistry and physics of lipids Vol. 203; pp. 46 - 53
• Main Authors: Heller, William T., Rai, Durgesh K.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.03.2017; Elsevier
• Subjects: 60 APPLIED LIFE SCIENCES; BASIC BIOLOGICAL SCIENCES; HIV Envelope Protein gp41 - chemistry; HIV Envelope Protein gp41 - metabolism; HIV-1 fusion peptide; Intrinsic curvature; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Molecular Structure; Small-angle neutron scattering; CD; Intrinsic curvature; POPS; FP; DLS; SLD; DMPS; P/L; d54-DMPC; TFE; POPG; Small-angle neutron scattering; SANS; POPC; HIV-1 fusion peptide; HC; DMPC; HG
• ISSN: 0009-3084; 1873-2941
• DOI: 10.1016/j.chemphyslip.2017.01.004

•Interaction of a derivative of the HIV-1 fusion peptide with DMPC:DMPS vesicles was studied.•The fusion peptide undergoes a concentration-dependent transition between an α-helix and a β-sheet.•The conformational transition of the peptide is accompanied by changes in the structure of the lipid bilayer vesicle. HIV-1, like other enveloped viruses, undergoes fusion with the cell membrane to infect it. Viral coat proteins are thought to bind the virus to the membrane and actively fuse the viral and cellular membranes together. The actual molecular mechanism of fusion is challenging to visualize, resulting in the use of model systems. Here, the bilayer curvature modifying properties of a synthetic variant of the HIV-1 gp41 fusion peptide with lipid bilayer vesicles composed of a mixture of dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylserine (DMPS) were studied. In 7:3 DMPC:DMPS vesicles made with deuterium-labeled DMPC, the peptide was observed to undergo a concentration-dependent conformational transition between an α-helix and an antiparallel β-sheet. Through the use of small-angle neutron scattering (SANS) and selective deuterium labeling, it was revealed that conformational transition of the peptide is also accompanied by a transition in the structure of the lipid bilayer. In addition to changes in the distribution of the lipid between the leaflets of the vesicle, the SANS data are consistent with two regions having different thicknesses. Of the two different bilayer structures, the one corresponding to the smaller area fraction, being ∼8% of the vesicle area, is much thicker than the remainder of the vesicle, which suggests that there are regions of localized negative curvature similar to what takes place at the point of contact between two membranes immediately preceding fusion.