Structural investigations on the ATP-synthase from chloroplasts

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The F-type ATP-synthase from chloroplasts couples ATP-synthesis/hydrolysis to a transmembrane proton transport. The ATP-synthase consists of two structurally distinct units, a membrane embedded Fo, which carries the proton translocation machinery, and an extrinsic F1, which accommodates the nucleotide binding sites. F1 and Fo are connected by a thinner connecting region with a central stalk and a peripheral stator. The enzyme works with a rotary mechanism, where proton transport causes rotation of a ring-like structure in Fo, which co-rotates the central stalk. The rotation of the stalk induces conformational changes in the nucleotide binding sites which are necessary for synthesis/hydrolysis. The detailed understanding of this mechanism is hampered by a lack of high resolution structural information. Atomic structures of complete ATP-synthases are still missing and most high resolution structural information is focussed on sub-complexes showing the soluble F1, whereas only little is known on the atomic structure of Fo and the peripheral stator. Therefore, it is our aim to determine an atomic structure of either the whole ATP-synthase from chloroplasts or sub-complexes containing parts of Fo or the peripheral connector using X-ray crystallography. To get a dynamic picture of catalysis the high resolution structural information will be combined with low resolution maps of the ATP-synthase in different conformational states, which will be derived from electron microscopic investigations.