title: Neither helix in the coiled coil region of the axle of F1-ATPase plays a significant role in torque production.
abstract: F(1)-ATPase is an ATP-driven rotary molecular motor in which the central gamma-subunit rotates inside the cylinder made of alpha(3)beta(3) subunits. The amino and carboxy termini of the gamma-subunit form the axle, an alpha-helical coiled coil that deeply penetrates the stator cylinder. We previously truncated the axle step by step, starting with the longer carboxy terminus and then cutting both termini at the same levels, resulting in a slower yet considerably powerful rotation. Here we examine the role of each helix by truncating only the carboxy terminus by 25-40 amino-acid residues. Longer truncation impaired the stability of the motor complex severely: 40 deletions failed to yield rotating the complex. Up to 36 deletions, however, the mutants produced an apparent torque at nearly half of the wild-type torque, independent of truncation length. Time-averaged rotary speeds were low because of load-dependent stumbling at 120 degrees intervals, even with saturating ATP. Comparison with our previous work indicates that half the normal torque is produced at the orifice of the stator. The very tip of the carboxy terminus adds the other half, whereas neither helix in the middle of the axle contributes much to torque generation and the rapid progress of catalysis. None of the residues of the entire axle played a specific decisive role in rotation.
authors: Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-Ku, Tokyo 169-8555, Japan.
authors: Mohammad Delawar
authors: MD
authors: Hossain
authors: Shou
authors: S
authors: Furuike
authors: Yasushi
authors: Y
authors: Maki
authors: Kengo
authors: K
authors: Adachi
authors: Toshiharu
authors: T
authors: Suzuki
authors: Ayako
authors: A
authors: Kohori
authors: Hiroyasu
authors: H
authors: Itoh
authors: Masasuke
authors: M
authors: Yoshida
authors: Kazuhiko
authors: K
authors: Kinosita
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D009038:Motion; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000648:ultrastructure*; D019415:Torque
chemical_list: D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases