Characterization of the water defect at the HIV-1 gp41 membrane spanning domain in bilayers with and without cholesterol using molecular simulations

• Published in: Biochimica et biophysica acta Vol. 1838; no. 5; pp. 1396 - 1405
• Main Authors: Baker, Michelle K., Gangupomu, Vamshi K., Abrams, Cameron F.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-05-2014
• Subjects: 1,2-Dipalmitoylphosphatidylcholine - chemistry; 1,2-Dipalmitoylphosphatidylcholine - metabolism; Amino Acid Sequence; Arginine - chemistry; Arginine - metabolism; Cell Membrane - chemistry; Cell Membrane - metabolism; Cholesterol - chemistry; Cholesterol - metabolism; HIV Envelope Protein gp41 - chemistry; HIV Envelope Protein gp41 - metabolism; HIV-1 - chemistry; HIV-1 - metabolism; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Membrane Fusion - physiology; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Membrane simulation; Metadynamics; Midspan arginine; Molecular dynamics; Molecular Dynamics Simulation; Molecular Sequence Data; Peptides - chemistry; Peptides - metabolism; Protein Structure, Secondary; Protein Structure, Tertiary; Snorkeling; Transmembrane; Water - chemistry; Water - metabolism; Molecular dynamics; Midspan arginine; Metadynamics; Membrane simulation; Transmembrane; Snorkeling
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/j.bbamem.2014.01.009

The membrane spanning domain (MSD) of human immunodeficiency virus 1 (HIV-1) envelope glycoprotein gp41 is important for fusion and infection. We used molecular dynamics (MD) simulations (3.4μs total) to relate membrane and peptide properties that lead to water solvation of the α-helical gp41 MSD's midspan arginine in pure dipalmitoylphosphatidylcholine (DPPC) and in 50/50 DPPC/cholesterol membranes. We find that the midspan arginine is solvated by water that penetrates the inner leaflet, leading to a so-called water defect. The water defect is surprisingly robust across initial conditions and membrane compositions, but the presence of cholesterol modulates its behavior in several key ways. In the cholesterol-containing membranes, fluctuations in membrane thickness and water penetration depth are localized near the midspan arginine, and the MSD helices display a tightly regulated tilt angle. In the cholesterol-free membranes, thickness fluctuations are not as strongly correlated to the peptide position and tilt angles vary significantly depending on protein position relative to boundaries between domains of differing thickness. Cholesterol in an HIV-1 viral membrane is required for infection. Therefore, this work suggests that the colocalized water defect and membrane thickness fluctuations in cholesterol-containing viral membranes play an important role in fusion by bringing the membrane closer to a stability limit that must be crossed for fusion to occur.
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•A water defect solvates midspan R694 of HIV-1 gp41 membrane-spanning domain (MSD).•Cholesterol tightly localizes the water defect and associated membrane thinning.•The water defect may bring the membrane closer to a stability limit.