This brief discusses the mechanism of functional expression of a protein or protein complex utilizing the ATP hydrolysis cycle or proton-motive force from a unique point of view focused on the roles of water. A variety of processes are considered such as the unidirectional movement of a linear-motor protein along a filament, insertion of an unfolded protein into a chaperonin and release of the folded protein from it, transport of diverse substrates across the membrane by a transporter, and directed rotation of the central subunit within a rotatory motor protein complex. These topics are discussed in a unified manner within the same theoretical framework. The author argues that water plays imperative roles in the functional expression of these molecular machines. A pivotal factor is the entropic force or potential originating from the translational displacement of water molecules coexisting with the molecular machines in the entire system.

Autorentext
Prof. Dr. Masahiro KinoshitaInstitute of Advanced Energy Kyoto University

Inhalt
Introduction.- Importance of Translational, Configurational Entropy of Water.- Molecular Machines.- Concluding Remarks: Mechanism of Functional Expression Common in the Molecular Machines.