title: Fluid mechanical matching of H+-ATP synthase subunit c-ring with lipid membranes revealed by 2H solid-state NMR.
abstract: The F(1)F(o)-ATP synthase utilizes the transmembrane H(+) gradient for the synthesis of ATP. F(o) subunit c-ring plays a key role in transporting H(+) through F(o) in the membrane. We investigated the interactions of Escherichia coli subunit c with dimyristoylphosphatidylcholine (DMPC-d(54)) at lipid/protein ratios of 50:1 and 20:1 by means of (2)H-solid-state NMR. In the liquid-crystalline state of DMPC, the (2)H-NMR moment values and the order parameter (S(CD)) profile were little affected by the presence of subunit c, suggesting that the bilayer thickness in the liquid-crystalline state is matched to the transmembrane hydrophobic surface of subunit c. On the other hand, hydrophobic mismatch of subunit c with the lipid bilayer was observed in the gel state of DMPC. Moreover, the viscoelasticity represented by a square-law function of the (2)H-NMR relaxation was also little influenced by subunit c in the fluid phase, in contrast with flexible nonionic detergents or rigid additives. Thus, the hydrophobic matching of the lipid bilayer to subunit c involves at least two factors, the hydrophobic length and the fluid mechanical property. These findings may be important for the torque generation in the rotary catalytic mechanism of the F(1)F(o)-ATPse molecular motor.
authors.affiliation: Institute for Protein Research, Osaka University, Yamadoaka, Suita 565-0871, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Struts
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Michael F
authors.initials: MF
authors.lastname: Brown
authors.forename: Hideo
authors.initials: H
authors.lastname: Akutsu
mesh_terms: D003198:Computer Simulation; D003903:Deuterium; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D044085:Microfluidics / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D009038:Motion; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D008051:Lipid Bilayers; D020409:Molecular Motor Proteins; D021122:Protein Subunits; D003903:Deuterium; D006180:Proton-Translocating ATPases