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Abstract

ATP synthase plays a crucial role in ATP production in all organisms. The F0 ring region of ATP synthase is rotated by protons translocated across the membranes in response to proton motive force (pmf)—a transmembrane energy source composed of the membrane potential (Δψ) and the proton concentration gradient (ΔpH) (Davis et al. 2017).Despite their conserved role and mechanism in ATP production, there is structural diversity in the number of transmembrane proteins, called c-subunits, that form the ring rotor. The c-ring stoichiometry differs among bacteria, animals, and photosynthetic organisms, from c8 in animal mitochondria (Watt et al. 2010) and c14 in plant chloroplasts (Seelert et al. 2000; Hahn et al. 2018) to c15 in the cyanobacteria Burkholderia platensis (Pogoryelov et al. 2005). The c-ring stoichiometry determines how many protons are required to generate one ATP molecule. An ATP synthase with a larger c-ring stoichiometry needs more protons per ATP synthesized, making ATP synthase less energy-efficient (Nesci et al. 2016; Cheuk and Meier 2021).