Dr. Alexander Hahn works at Max-Planck-Institute of Biophysics in Frankfurt, Germany.
The F-type ATP synthase (F1Fo) in the thylakoid membranes is responsible for the bulk ATP production of plants, cyanobacteria and green algae. It utilizes the proton-motive force across the thylakoid membrane to generate ATP from ADP and inorganic phosphate by rotary catalysis. The basic architecture can be subdivided in three functional elements: The Fo-rotor complex, the catalytic F1 complex and the peripheral stalk. While all major functional aspects of rotary ATP synthases are preserved throughout all kingdoms of life, the chloroplast ATP synthase (CF1Fo) has a unique dithiol redox switch, formed by the insertion of a short amino acid loop in the central rotor subunit gamma. This redox switch is thought to keep CF1Fo in an inactive state during phases of light deprivation. We determined the structure of the chloroplast ATP synthase isolated from Spinach by single particle cryo-EM at 4.2 Å. We identified three distinct conformations which represent the three catalytic positions within the binding change mechanism. We were able to build a complete CF1Fo model that includes amino acide side chain information about the unique dithiol redox switch of the gamma subunit. The complete structure allows a comprehensive description of this bacterial-type ATP synthase with respect to the underlying rotary mechanism and its redox regulation in plant chloroplasts.