ATPases are a class of enzymes that catalyze the decomposition of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life.
Adenosine triphosphate (ATP) is the primary energy "currency" in most living organisms. Storing readily-available energy in the form of a chemical bond, ATP delivers it to a reaction site and releases it in the process of hydrolysis, providing an energy supply for enzymatic reactions and biomechanical processes. ATP synthase is a large (about 100,000 atoms) protein, which includes a transmembrane F0 unit coupled to a solvent-exposed F1 unit via a central stalk gamma. The F0 unit utilizes a transmembrane electrochemical potential (proton motive force), converting it into the mechanical energy of the stalk rotation. The rotation leads to cyclic conformational changes in the catalytic sites in the F1 unit, thereby driving ATP synthesis. ATP synthase can also function in the reverse direction, hydrolyzing ATP and utilizing the released energy to pump protons across the membrane. This reversibility, along with the nearly 100% efficiency and the recently discovered, remarkably symmetric structure (1997 Nobel Prize in Chemistry), makes ATP synthase a perfect system for exploring interconversion between mechanical and electrochemical energy in molecular motors.