title: Structural plasticity in the topology of the membrane-interacting domain of HIV-1 gp41.
abstract: We use a number of computational and experimental approaches to investigate the membrane topology of the membrane-interacting C-terminal domain of the HIV-1 gp41 fusion protein. Several putative transmembrane regions are identified using hydrophobicity analysis based on the Wimley-White scales, including the membrane-proximal external region (MPER). The MPER region is an important target for neutralizing anti-HIV monoclonal antibodies and is believed to have an interfacial topology in the membrane. To assess the possibility of a transmembrane topology of MPER, we examined the membrane interactions of a peptide corresponding to a 22-residue stretch of the MPER sequence (residues 662-683) using fluorescence spectroscopy and oriented circular dichroism. In addition to the previously reported interfacial location, we identify a stable transmembrane conformation of the peptide in synthetic lipid bilayers. All-atom molecular dynamics simulations of the MPER-derived peptide in a lipid bilayer demonstrate a stable helical structure with an average tilt of 24 degrees, with the five tryptophan residues sampling different environments inside the hydrocarbon core of the lipid bilayer, consistent with the observed spectral properties of intrinsic fluorescence. The degree of lipid bilayer penetration obtained by computer simulation was verified using depth-dependent fluorescence quenching of a selectively attached fluorescence probe. Overall, our data indicate that the MPER sequence can have at least two stable conformations in the lipid bilayer, interfacial and transmembrane, and suggest a possibility that external perturbations can switch the topology during physiological functioning.
authors: Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas.
authors: Alexander
authors: A
authors: Kyrychenko
authors: Department of Chemistry, University of California, Irvine, California.
authors: J Alfredo
authors: JA
authors: Freites
authors: Department of Biochemistry, Tulane University School of Medicine, New Orleans, Louisiana.
authors: Jing
authors: J
authors: He
authors: Department of Chemistry, University of California, Irvine, California.
authors: Douglas J
authors: DJ
authors: Tobias
authors: Department of Biochemistry, Tulane University School of Medicine, New Orleans, Louisiana.
authors: William C
authors: WC
authors: Wimley
authors: Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas. Electronic address: aladokhin@kumc.edu.
authors: Alexey S
authors: AS
authors: Ladokhin
mesh_terms: D000595:Amino Acid Sequence; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D015700:HIV Envelope Protein gp41; D008051:Lipid Bilayers; C514787:gp41 protein, Human immunodeficiency virus 1