The Stochastic Model of F_1-ATPase Molecular Motor Functioning

摘要

In continuation of, this work is devoted to the study of the energy characteristics of the F_1ATPase-substrate complex. The results of calculations of the electrostatic energy in the enzyme-substrate complex are presented in the first part. In calculations, we take into account the electrostatic interactions between the charged groups of the substrate (MgATP) and reaction products (MgADP and P_i) and charged amino acid residues of the α_3β_3γ complex that correspond to various conformations of the enzyme. The hydrolysis of ATP in the catalytic site leads to coordinated conformational changes in α, β subunits and to ordered rotation of γ subunit located in the center of F_1ATPase complex. The calculations show that the energetically favorable process involving MgATP binding at the catalytic site in the "open" conformation initiates γ subunit rotation followed by the hydrolysis in the other (tight) catalytic site. In the second part, we propose the simplest stochastic model describing the ordered rotation of γ subunit (the rotor of F_1-ATPase molecular motor). In the model we take into account the electrostatic interaction using the results of the previous calculations. We employ experimentally obtained dynamic parameters from. The model takes into account the thermal fluctuations of the bath and the random processes of the substrate binding and the escape of the reaction products.