Proton Diffusion and the Bioenergies of Enzymes in Membranes

SYNTHESIS OF A SELF‐CONTAINED CONCEPT OF THE MOLECULAR MECHANISM OF ENERGY INTERCONVERSION BY H+‐TRANSPORTING ATP SYNTHASE

“…The primary purpose of our present work has been to probe into the tenability of the paradigm on the high energy-carrier function of ATP on the basis of the current knowledge of the molecular structure and the thinking on the mechanism of Hftransporting ATP synthase as described in a series of differently focused reviews (P. Mitchell, 1981 ; P. Mitchell & Koppenol, 1982;Amzel & Pedersen, 1983;Senior & Wise, 1983;Futai & Kanazawa, 1983;Cross et al, 1984; R. Mitchell, 1984; Vignais & Satre, 1984; Kagawa, 1984;Hatefi, 1985; P. Mitchell, 1 9 8 5~; Williams, 1985;Slater, 1987;Boyer, 1987;Ysern et al, 1988; Matsuno-Yagi & Hatefi, 1988;Senior, 1988;Williams, 1988;Skulachev, 1988;Boyer, 1989;Futai et al, 1989; Senior, 1990; Graber, 1990;Stein & Lauger, 1990; Fillingame, 1990;Penefsky & Cross, 1991 ;Hatefi & Matsuno-Yagi, 1992; Issartel et al, Cross, 1992;Nicholls & Ferguson, 1992;Boyer, 1993;Pedersen, 1993). Their perusal shows that various mechanistic essentials of the enzyme, linked with our inquiry, have not specifically been explored.…”

“…T h e y subunit also appears to form a rod which extends through the entire F, and to be an 3-helix (Abraham et al, 1993); the Cterminal sequence of the y subunit is conserved, which might indicate a close interaction with the highly conserved a and p subunits. Regarding the energization of F,,F,, Williams (1985) considered it a simple possibility that the protons, as they accumulate, cause tension in the b subunit by altering the twist of the helices; at some particular proton loading, some of the twisting energy could be transmitted to F,-p while the protons become released. At any event, the a-helices can be assumed to provide by H+ bondings the proton path across F, (cf.…”

“…As stated by Williams (1988), in I 96 I Mitchell and Williams proposed independently that energy transduction from light or oxidation-reduction reactions to give A T P (pyrophosphate energy) is mediated by proton concentration gradients. Moreover, they agreed that one could view the driving force as virtually an equilibrium between a proton chemical potential energy and a chemical bond Gibbs energy of A T P (see Williams, 1988).…”

“…As stated by Williams (1988), in I 96 I Mitchell and Williams proposed independently that energy transduction from light or oxidation-reduction reactions to give A T P (pyrophosphate energy) is mediated by proton concentration gradients. Moreover, they agreed that one could view the driving force as virtually an equilibrium between a proton chemical potential energy and a chemical bond Gibbs energy of A T P (see Williams, 1988). These elementary insights appeared to have been invalidated by the observations that proton-flow energy is not required for the synthesis of A T P from enzyme-bound A D P and P i ; the energy rather appeared to be essentially spent for the expulsion of spontaneously formed A T P from the catalytic centre (for a comprehensive documentation see Boyer, 1992).…”