title: Preliminary estimation of rotary torque produced by proton-motive force in fully functional F0F1-ATPase.
abstract: F(0)F(1)-ATPase is a rotary molecular motor. It is well known that the rotary torque is generated by ATP hydrolysis in F(1) but little is known about how it produces the proton-motive force (PMF) in F(0). Here a cross-linking approach was used to estimate the rotary torque produced by PMF. Three mutant E. coli strains were used in this study: SWM92 (deltaW28L F(0)F(1), as control), MM10 (alphaP280CgammaA285C F(0)F(1)) and PP2 (alphaA334C/gammaL262C F(0)F(1)). The oxidized inner membranes from mutant MM10 having a disulfide bridge in the top of gamma subunit exhibited good ATP synthesis activity, while the oxidized PP2 inner membranes having a disulfide bridge in the middle of gamma subunit synthesized ATP very poorly. We conclude that the rotary torque generated by PMF is sufficient to uncoil the alpha-helix in the top of gamma subunit (MM10) and to overcome the Ramachandran activation barriers (25-30 kJ/mol, i.e. about 40-50pNnm), but cannot cleave the disulfide bond in the middle of the gamma subunit (200 kJ/mol, i.e. 330pNnm) (PP2). Consequently a preliminary estimation is that the rotary torque generated by PMF in the fully functional F(0)F(1) motor is greater than 40-50pNnm but less than 330pNnm.
authors.affiliation: The Key Laboratory of Biomedial Information Engineering of Education Ministry, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Liu
authors.forename: Yuanbo
authors.initials: Y
authors.lastname: Cui
authors.forename: Chuanfang
authors.initials: C
authors.lastname: Chen
authors.forename: Bo
authors.initials: B
authors.lastname: Lai
authors.forename: Jiachang
authors.initials: J
authors.lastname: Yue
authors.forename: Zhenxi
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D003432:Cross-Linking Reagents; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D018892:Proton-Motive Force / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012399:Rotation; D019415:Torque
chemical_list: D003432:Cross-Linking Reagents; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases