title: Torque, chemistry and efficiency in molecular motors: a study of the rotary-chemical coupling in F1-ATPase.
abstract: Detailed understanding of the action of biological molecular machines must overcome the challenge of gaining a clear knowledge of the corresponding free-energy landscape. An example for this is the elucidation of the nature of converting chemical energy to torque and work in the rotary molecular motor of F1-ATPase. A major part of the challenge involves understanding the rotary-chemical coupling from a non-phenomenological structure/energy description. Here we focused on using a coarse-grained model of F1-ATPase to generate a structure-based free-energy landscape of the rotary-chemical process of the whole system. In particular, we concentrated on exploring the possible impact of the position of the catalytic dwell on the efficiency and torque generation of the molecular machine. It was found that the experimentally observed torque can be reproduced with landscapes that have different positions for the catalytic dwell on the rotary-chemical surface. Thus, although the catalysis is undeniably required for torque generation, the experimentally observed position of the catalytic dwell at 80° might not have a clear advantage for the force generation by F1-ATPase. This further implies that the rotary-chemical couplings in these biological motors are quite robust and their efficiencies do not depend explicitly on the position of the catalytic dwells. Rather, the specific positioning of the dwells with respect to the rotational angle is a characteristic arising due to the structural construct of the molecular machine and might not bear any clear connection to the thermodynamic efficiency for the system.
authors.affiliation: Department of Chemistry,University of Southern California,418 SGM Building,3620 McClintock Avenue,Los Angeles,CA 90089-1062,USA.
authors.forename: Shayantani
authors.initials: S
authors.lastname: Mukherjee
authors.affiliation: Department of Chemistry,University of Southern California,418 SGM Building,3620 McClintock Avenue,Los Angeles,CA 90089-1062,USA.
authors.forename: Ram Prasad
authors.initials: RP
authors.lastname: Bora
authors.affiliation: Department of Chemistry,University of Southern California,418 SGM Building,3620 McClintock Avenue,Los Angeles,CA 90089-1062,USA.
authors.forename: Arieh
authors.initials: A
authors.lastname: Warshel
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D055592:Biophysical Phenomena; D002384:Catalysis; D006868:Hydrolysis; D020409:Molecular Motor Proteins / Q000737:chemistry*; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D012399:Rotation; D013696:Temperature; D013816:Thermodynamics; D019415:Torque
chemical_list: D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases
keywords: F0F1-ATP synthase; bioenergetics; conformational surface; rotary-chemical surface