title: Membrane-induced alteration of the secondary structure in the SWAP-70 pleckstrin homology domain.
abstract: Differences in the conformation of the pleckstrin homology (PH) domain of switch-associated protein-70 (SWAP-70) in solution and at the lipid bilayer membrane surface were examined using CD, fluorescence and NMR spectroscopy. Intracellular relocalization of SWAP-70 from the cytoplasm to the plasma membrane and then to the nucleus is associated with its cellular functions. The PH domain of SWAP-70 contains a phosphoinositide-binding site and a nuclear localization signal, which localize SWAP-70 to the plasma membrane and nucleus, respectively. CD and fluorescence spectra showed that a significant conformational alteration involving formation of disordered structure occurs when the PH domain binds to D-myo-phosphatidylinositol 3,4,5-trisphosphate or D-myo-phosphatidylinositol 4,5-bisphosphate embedded in lipid bilayer vesicles. NMR spectra indicate that Ala and Trp residues located in the C-terminal α-helix of the PH domain undergo conformational alterations to form a disordered structure at the vesicle surface. These conformational alterations were not induced by association with inositol 1,3,4,5-tetrakisphosphate in solution or coexistence of phosphatidylcholine vesicles. Interaction with the plane of the lipid bilayer via association with the phosphoinositides is required for the unfolding of the C-terminal α-helix of the PH domain. The unwinding of the C-terminal α-helix could regulate the functions of SWAP-70 at the plasma membrane surface.
authors.affiliation: Graduate School of Life Science, University of Hyogo, Harima Science Garden City, Kouto 3-chome, Kamigori, Hyogo 678-1297, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Tokuda
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Kawai
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
authors.forename: Takahisa
authors.initials: T
authors.lastname: Ikegami
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yagisawa
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Fukui
authors.forename: Satoru
authors.initials: S
authors.lastname: Tuzi
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000737:chemistry*; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry*; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry*; D010716:Phosphatidylinositols / Q000737:chemistry; D010767:Phosphorylcholine / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D008051:Lipid Bilayers; D015778:Minor Histocompatibility Antigens; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010716:Phosphatidylinositols; C491873:SWAP70 protein, human; D010767:Phosphorylcholine