Abstract
Driven by transmembrane electrochemical ion gradients, F-type ATP synthases are the primary source of the universal energy currency, adenosine triphosphate (ATP), throughout all domains of life. The ATP synthase found in the thylakoid membranes of photosynthetic organisms has some unique features not present in other bacterial or mitochondrial systems. Among these is a larger-than-average transmembrane rotor ring and a redox-regulated switch capable of inhibiting ATP hydrolysis activity in the dark by uniquely adapted rotor subunit modifications. Here, we review recent insights into the structure and mechanism of ATP synthases specifically involved in photosynthesis and explore the cellular physiological consequences of these adaptations at short and long time scales.
Highlights
Cellular life depends on the energy that is powered by sun light
The light-dependent reactions of photosynthesis involve a series of large, macromolecular complexes, which are capable of harvesting light energy to split water molecules releasing electrons for the reduction in NADP+ into NADPH and releasing protons (H+) into the thylakoid lumen generating the proton-motive force, pmf, required for adenosine triphosphate (ATP) synthesis
The four large protein complexes involved in the production of NADPH and ATP are photosystem II, cytochrome b6f, photosystem I and ATP synthase
Summary
Cellular life depends on the energy that is powered by sun light. Its direct users are plants, algae and some clades of bacteria, e.g. cyanobacteria and purple bacteria. The ATP synthase can operate in reverse, converting energy from ATP hydrolysis and pumping ions across the membrane to generate a pmf [7]. Compared with most bacterial or mitochondrial ATP synthases this is a rather large stoichiometry, leading to an ion-to-ATP ratio of 4.7 in plants and 4.3–5.0 in cyanobacteria.
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