Theoretical study on the ATP hydrolysis mechanism of HisP protein, the ATP-binding subunit of ABC transporter

ATP binding subunit is known as a subunit of ABC transporter, providing energy through the binding of ATP with the subunit and the subsequent hydrolysis reaction of the bound ATP. In this study, density functional theory (DFT) method was used to study the ATP hydrolysis reaction in HisP protein, an ATP binding subunit of Histidine permease HisQMP₂, by considering the ATP binding site, especially the γ-phosphate group, surrounding residues and water molecules. Based on DFT calculations, we proposed that ATP hydrolysis is initiated by the formation of Mg²⁺ mediated coordinate complex followed by the nucleophilic attack of a single water molecule (Water437) on the γ-phosphate; the hydrolysis product ADP acts as a leaving group. The transition state structure was determined by an approximate saddle-point search.