2020 - Energy Coupling in Cation-Pumping Pyrophosphatase—Back to Mitchell
SURFE²R N1 publication in Frontiers in Plant Science (2020)
Frontiers in Plant Science (2020) 11: 107 doi: 10.3389/fpls.2020.00107
Those of a certain age may remember (and their younger colleagues can read) accounts of the vivid debate in the 1970s surrounding the coupling mechanism involved in oxidative and photo phosphorylation. By that time, Mitchell's chemiosmotic hypothesis had already gained credence, and the debated issue was how a transmembrane H+ potential difference drives ATP synthesis by Ftype ATP synthases. The major mechanisms that were considered assumed that the membrane (Fo) and peripheral (F1) parts were functionally connected in different ways. Peter Mitchell proposed a “direct coupling” mechanism in which protons are translocated through Fo into the catalytic site of F1, where they participate directly in ADP phosphorylation and form water as the second product (Mitchell, 1974). Paul Boyer, the proponent of the main competing mechanism, advocated an “indirect coupling” mechanism (successively termed “alternating site”, “binding change”, or “rotational”) that implied that protons transfer their energy to the catalytic site indirectly, via distant conformational strain (Boyer, 1997). The debate was resolved in favor of Boyer's mechanism when it became clear that the alternative mechanism is inconsistent with H+ /ATP stoichiometry and, finally, when the three-dimensional structure of the F-ATPase was determined (Abrahams et al., 1994).