Diversity in P-loop Structure of A-ATP Synthase

Authors 13B1 13C1 ATP synthase and ATPase are the key components in energy utilization in cells. They are essentially the turbines in powerhouse to create energy in the form of ATP or use ATP as energy to drive cellular activities. P-loop is a common motif in ATP and GTP binding proteins, including ATP synthase and ATPase, and its conformation change is critical in A/GTP utilization. Prof. Grüber’s group solves several structures of A-ATP synthases. It contributes to our knowledge of P-loop. Differences as small as 3 amino acids in the P-loop sequence change its conformation and have a profound impact on its effectiveness. It demonstrates how nature optimizes biological activities down to such tiny details. A-, F-ATP synthases and V-ATPases are fascinating enzymes, which arose from a common ancestor and are present in every life form. They are essential for life and are known as the coupling factors which convert the electrochemical ion gradient across the membrane to the synthesis of adenosine triphosphate (ATP) and vice versa. F1FO ATP synthases (F-ATP synthases) are responsible for the generation of ATP in the eukaryotic and prokaryotic cells, while in archaea the A1AO ATP synthases use the Hand/or Na-gradient across the membrane to drive ATP production. Largely ATP synthases use the ion motive force for generating ATP, whereas the vacuolar ATPases (V-ATPase) of eukaryotic cells hydrolyze ATP to generate proton motive force. The variations in the subunit composition drive the difference in their functions. The A-ATP synthase is composed of nine subunits in a proposed stoichiometry of A3 : B3 : C : D : E : F : H2 : a : cx while the related bacterial F-ATP synthase has eight subunits (α3 : β3 : γ : δ : ε : a : b2 : cx) and the eukaryotic V-ATPase has thirteen subunits (A3 : B3 : C : D : E : F : G2 : Hx : a : d : cx : c’x : c’’x). 2