CF0CF1ATPsyntaasi

CF0CF1ATPsyntaasi, also known as chloroplast F0F1 ATP synthase, is a membrane-bound enzyme complex that produces ATP in photosynthetic organisms. It is located in the thylakoid membranes of chloroplasts and in analogous membranes of cyanobacteria. The enzyme comprises two functional sectors: CF0, the membrane-embedded proton channel, and CF1, the soluble catalytic head. A proton motive force generated by the light-driven electron transport chain drives protons back across the thylakoid membrane through CF0, causing rotation of the c-ring and the attached central stalk. This rotary motion induces conformational changes in CF1 that catalyze the synthesis of ATP from ADP and inorganic phosphate.

CF1 contains the catalytic alpha and beta subunits arranged in a hexameric core surrounding the central gamma subunit, with beta subunits housing the active sites. The gamma subunit acts as a rotor that transmits mechanical energy from CF0 to drive catalysis. CF0 includes subunits that form the proton channel and rotor attachments to the c-ring. The enzyme is reversible: in conditions where the proton motive force is low or in darkness, it can hydrolyze ATP to pump protons, helping regulate the proton gradient.

Genetic organization varies: many subunits are encoded by the plastid genome, while others are encoded in the nuclear genome and imported into chloroplasts. Proper assembly requires chaperones and assembly factors. Functionally, CF0CF1 ATPsyntaasi links the light reactions of photosynthesis to energy storage, supplying ATP for carbon fixation and other metabolic processes within the chloroplast.

The enzyme is highly conserved across plants, algae, and cyanobacteria and has been central to studies of rotary ATP synthases and energy metabolism.