Electrostatic interactions at the catalytic sites of F₁-ATPaSe

The first part of the paper is a short review of studies addressing the mechanisms of F_oF₁-type ATP synthases. In animal mitochondria, plant chloroplasts, and bacteria, F_oF₁ ATP synthases are reversible rotary molecular machines that utilize the energy of the transmembrane proton electrochemical potential gradient to catalyze ATP synthesis from ADP and inorganic phosphate P_i. Their distinguishing feature is that α and β subunits undergo significant conformational changes during rotor movement. The second part of lhe paper presents our calculations of the contributions from electrostatic interactions of the charged groups of the substrate (MgATP) and reaction products (MgADP and P_i) with the charged amino acid residues of the enzyme (oligomeric α₃β₂γ complex of bovine mitochondrial F₁-ATPase) to the energy changes associated with substrate binding and hydrolysis at the catalytic sites situated at the α and β subunit interface. In calculations, the conformalional changes of α and β subunits during a catalytic cycle of ATP hydrolysis were assumed to be associated with unidirectional rotation of the central γ subunit. The estimates obtained are consistent with the idea that the energy-favorable process of ATP binding to an "open" catalytic site of F ₁-ATPase initiates the rotation of the γ subunit followed by ATP hydrolysis in another ("closed") catalytic site of the enzyme.