Structure of the gamma-epsilon complex of ATP synthase

ATP synthases (FlFo-ATPases) use energy released by the movement of protons down a transmembrane electrochemical gradient to drive the synthesis of AT P, the universal biological energy currency. Proton flow through F-o drives rotation of a ring of c-subunits and a complex of the gamma and epsilon -s ubunits, causing cyclical conformational changes in F-l that are required f or catalysis. The crystal structure of a large portion of F-l has been reso lved. However, the structure of the central portion of the enzyme, through which conformational changes in F-l are communicated to F-l has until now r emained elusive. Here we report the crystal structure of a complex of the e psilon -subunit and the central domain of the gamma -subunit refined at 2.1 Angstrom resolution. The structure reveals how rotation of these subunits causes large conformational changes in F-l and thereby provides new insight s into energy coupling between F-o and F-l.