The universal fuel of cellular processes is adenosine triphosphate or ATP. In some bacteria, algae and plants, the energy stored in ATP comes from photosynthesis. In other bacteria and in all animals, the energy for ATP synthesis from ADP + Pi comes from the breakdown of foodstuffs, with the bulk of the energy transformation ocurring in a process called oxidative phosphorylation. The enzyme responsible for synthesis of ATP in photosynthesis and in oxidative phosphorylation, the ATP synthase, is a large multisubunit complex associated with the plasma membrane in bacteria, the inner membrane in mitochondria and the thylakoid membrane in chloroplasts. The ATP synthase from all of these sources is structurally similar, with a water soluble part extrinsic to the bilayer (F1 part) and transmembrane sector (FO part). Besides making ATP, synthase hydrolyzes ATP in a way that conserves the energy in the high energy phosphoryl bond for coupled transport processes. How this ATP synthase functions is unclear. To get at this question we are proposing a structure determination of the large protein complex. Our plan is to use electron microscopy of two- dimensional crystals of F1 and single particle analysis of F1 and F1F0 in combination to obtain a three-dimensional structure of the entire complex to 20-25A resolution. This low resolution structure will be used as a framework in which to locate individual subunits and functionally important sites including nucleotide binding sites.
