Polymorphism and interactions of a viral fusion peptide in a compressed lipid monolayer.
With a view toward possible new insights into viral fusion mechanisms, we have investigated the HIV-1 gp41 fusion peptide in a monomolecular film of the biomembrane lipid palmitoyloleoylphosphatidylcholine. Its surface activity at an air/water interface was measured under equilibrium conditions, using the conventional Langmuir trough technique. Through a novel thermodynamic analysis, the partial molecular area of the peptide in the lipid moiety could be determined as a function of the lateral pressure and the interfacial peptide/lipid ratio. This indicates an orientation of the peptide backbone parallel to the lipid hydrocarbon tails. The molecular area decreases significantly upon monolayer compression, suggesting a conformational transition from a somewhat compact configuration to a more extended, presumably beta-strand structure when a lipid packing density is approached that is generally believed to mimic the physical state of a biological membrane. Up to a lateral pressure of approximately 15 mN/m, practically all peptide inserts into the lipid monolayer. At higher compression a distinct partitioning into the aqueous subphase is observed. Under these conditions the data also reflect a strong aggregation of the lipid-associated peptide. Beyond a critical peptide/lipid ratio, the peptide's area requirement was found to become substantially enhanced, possibly because of the formation of water-filled pores.
Schwarz
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Department of Biophysical Chemistry, Biocenter of the University, University of Basel, CH-4056 Basel, Switzerland. schwarzg@ubaclu.unibas.ch
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D000595:Amino Acid Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics; D015497:HIV-1 / Q000737:chemistry / Q000235:genetics; D008561:Membrane Fusion; D008563:Membrane Lipids / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D010713:Phosphatidylcholines / Q000737:chemistry; D011110:Polymorphism, Genetic; D013499:Surface Properties; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics
D015700:HIV Envelope Protein gp41; D008563:Membrane Lipids; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D014760:Viral Fusion Proteins; C028694:1-palmitoyl-2-oleoylphosphatidylcholine