title: Structural characteristics of yeast F1-ATPase before and after 16-degree rotation of the γ subunit: theoretical analysis focused on the water-entropy effect.
abstract: We have recently proposed a novel picture of the rotation mechanism for F(1)-ATPase [T. Yoshidome, Y. Ito, M. Ikeguchi, and M. Kinoshita, J. Am. Chem. Soc. 133, 4030 (2011)]. In the picture, the asymmetric packing in F(1)-ATPase, originating from the water-entropy effect, plays the key role in the rotation. Here, we analyze the differences between the experimentally determined structures of yeast F(1)-ATPase before and after 16° rotation of the γ subunit with the emphasis on the water-entropy effect. For each of these structures, we calculate the hydration entropies of three sub-complexes comprising the γ subunit, one of the β subunits, and two α subunits adjacent to them. The β(E), β(TP), and β(DP) subunits are involved in sub-complexes I, II, and III, respectively. The calculation is performed using a hybrid of the angle-dependent integral equation theory combined with the molecular model for water and the morphometric approach. The absolute value of the hydration entropy is in the following order: sub-complex I > sub-complex II > sub-complex III. The packing efficiency of the sub-complex follows the opposite order. The rotation gives rise to less efficient packing in sub-complex III and a corresponding water-entropy loss. However, the other two sub-complexes, accompanying water-entropy gains, become more efficiently packed. These results are consistent with our picture of the rotation mechanism, supporting its validity. The water-entropy analysis shows that the interfaces of α(DP)-β(DP) and α(E)-β(E) become more open after the rotation, which is in accord with the experimental observation.
authors: Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors: Takashi
authors: T
authors: Yoshidome
authors: Yuko
authors: Y
authors: Ito
authors: Nobuyuki
authors: N
authors: Matubayasi
authors: Mitunori
authors: M
authors: Ikeguchi
authors: Masahiro
authors: M
authors: Kinoshita
mesh_terms: D019277:Entropy; D021122:Protein Subunits / Q000737:chemistry*; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology*; D014867:Water / Q000737:chemistry*
chemical_list: D021122:Protein Subunits; D014867:Water; D006180:Proton-Translocating ATPases