On the Mechanism of ATP Hydrolysis in ABC Transporter TAP, 2015
Adenosine triphosphate (ATP) is the energy currency molecule in the cell, and its hydrolysis is one of the most fundamental chemical reactions in biological systems. One example of a protein family that requires ATP binding and hydrolysis for function are the ATP-binding cassette transporters (TAP). In order to study the ATP hydrolysis inside TAP, a hybrid quantum mechanics / molecular mechanics (QM/MM) approach was used to describe the hydrolysis reaction by means of density functional theory (DFT) and the rest of the system by means of a classical force field.
All examined mechanisms (associative, dissociative, concerted, glutamate-catalyzed and histidine-catalyzed) failed to capture the exothermicity of ATP hydrolysis, in line with previous QM/MM studies. Due to computational costs, only one water molecule was included in the QM subsystem for the nucleophilic attack, excluding a possible mechanism involving proton wires with several waters. Therefore, including more water molecules in the QM subsystem could provide a more realistic picture and hence, could help in understanding the power stroke of ABC transporters.
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