title: Probing the U-shaped conformation of caveolin-1 in a bilayer.
abstract: Caveolin induces membrane curvature and drives the formation of caveolae that participate in many crucial cell functions such as endocytosis. The central portion of caveolin-1 contains two helices (H1 and H2) connected by a three-residue break with both N- and C-termini exposed to the cytoplasm. Although a U-shaped configuration is assumed based on its inaccessibility by extracellular matrix probes, caveolin structure in a bilayer remains elusive. This work aims to characterize the structure and dynamics of caveolin-1 (D82-S136; Cav182-136) in a DMPC bilayer using NMR, fluorescence emission measurements, and molecular dynamics simulations. The secondary structure of Cav182-136 from NMR chemical shift indexing analysis serves as a guideline for generating initial structural models. Fifty independent molecular dynamics simulations (100 ns each) are performed to identify its favorable conformation and orientation in the bilayer. A representative configuration was chosen from these multiple simulations and simulated for 1 μs to further explore its stability and dynamics. The results of these simulations mirror those from the tryptophan fluorescence measurements (i.e., Cav182-136 insertion depth in the bilayer), corroborate that Cav182-136 inserts in the membrane with U-shaped conformations, and show that the angle between H1 and H2 ranges from 35 to 69°, and the tilt angle of Cav182-136 is 27 ± 6°. The simulations also reveal that specific faces of H1 and H2 prefer to interact with each other and with lipid molecules, and these interactions stabilize the U-shaped conformation.
authors.affiliation: Department of Molecular Biosciences and Center for Bioinformatics, The University of Kansas, Lawrence, Kansas.
authors.forename: Huan
authors.initials: H
authors.lastname: Rui
authors.affiliation: Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania.
authors.forename: Kyle T
authors.initials: KT
authors.lastname: Root
authors.affiliation: Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania.
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania. Electronic address: kjg206@lehigh.edu.
authors.forename: Kerney Jebrell
authors.initials: KJ
authors.lastname: Glover
authors.affiliation: Department of Molecular Biosciences and Center for Bioinformatics, The University of Kansas, Lawrence, Kansas. Electronic address: wonpil@ku.edu.
authors.forename: Wonpil
authors.initials: W
authors.lastname: Im
mesh_terms: D000595:Amino Acid Sequence; D051242:Caveolin 1 / Q000737:chemistry* / Q000378:metabolism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D051242:Caveolin 1; D008051:Lipid Bilayers; D004134:Dimyristoylphosphatidylcholine