title: Physicochemical studies of bacteriorhodopsin reconstituted in partially fluorinated phosphatidylcholine bilayers.
abstract: A membrane protein bacteriorhodopsin (bR) that is successfully reconstituted in liposome of a novel partially fluorinated analog of dimyristoylphosphatidylcholine (DMPC) with the perfluorobutyl segments in the myristoyl groups, diF4H10-PC, has been investigated by some spectroscopic and X-ray diffraction techniques to clarify effects of substitution of nine hydrogen atoms by fluorine atoms on structural and physical properties of the membrane protein by comparison with the previous results on proteoliposome of bR and DMPC. Below the gel-to-liquid crystalline phase transition of diF4H10-PC bilayer, bR molecules adopt the two-dimensional lattice structure of trimers as the structural unit and show a photocycle very similar to that of native purple membrane like reconstituted bR in DMPC liposome in the gel phase. Even upon heating up to temperatures well above the phase transition, the nativelike functional reconstitution and higher structural stability of bR molecules in diF4H10-PC liposome are retained, which strikingly contrasts with lipid phase transition-induced disaggregation of protein molecules and light-induced denaturation in DMPC liposome. Greater membrane rigidity and low affinity between bR and fluorinated lipid molecules are proposed as a driving force for keeping nativelike properties of bR molecules in diF4H10-PC liposome even in the fluid phase.
authors.affiliation: Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Yoshino
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikukawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takagi
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Hideki
authors.initials: H
authors.lastname: Amii
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Baba
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kanamori
authors.forename: Masashi
authors.initials: M
authors.lastname: Sonoyama
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D002627:Chemistry, Physical; D005461:Fluorine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D015394:Molecular Structure; D010713:Phosphatidylcholines / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D005461:Fluorine; D001436:Bacteriorhodopsins