A point mutation in the ATP synthase of Rhodobacter capsulatus results in differential contributions of DeltapH and Deltaphi in driving the ATP synthesis reaction

Abstract

The interface between the c-subunit oligomer and the a subunit in the F 0 sector of the ATP synthase is believed to form the core of the rotating motor powered by the protonic flow. Besides the essential cAsp61 and aArg210 residues (Escherichia coli numbering), a few other residues at this interface, although nonessential, show a high degree of conservation, among these aGlu219. The homologous residue aGlu210 in the ATP synthase of the photosynthetic bacterium Rhodobacter capsulatus has been substituted by a lysine. Inner membranes prepared from the mutant strain showed approximately half of the ATP synthesis activity when driven both by light and by acid-base transitions. As estimated with the ACMA assay, proton pumping rates in the inner membranes were also reduced to a similar extent in the mutant. The most striking impairment of ATP synthesis in the mutant, a decrease as low as 12 times as compared to the wild-type, was observed in the absence of a transmembrane electrical membrane potential (Du) at low transmembrane pH difference (DpH). Therefore, the mutation seems to affect both the mechanism responsible for coupling F 1 with proton translocation by F 0 , and the mechanism determining the relative contribution of DpH and Du in driving ATP synthesis.

Dodecamer rotor ring defines H + /ATP ratio for ATP synthesis of prokaryotic V-ATPase from Thermus thermophilus

“…In a study using F o F 1 from chloroplasts, ATP was synthesized after an acidbase transition in the absence of ⌬⌿ (28). There were several lines of evidence indicating that both ⌬pH and ⌬⌿ are capable of driving the ATP synthesis reaction (14,(27)(28)(29). However, Kaim and Dimroth (15) have reported that the ATP synthesis reaction by E. coli F o F 1 depends on ⌬⌿ and could not be energized by ⌬pH only (15).…”

ATP synthases: structure, function and evolution of unique energy converters

“…Extensive mutagenesis studies revealed that residues Arg-210, His-245 and Glu-219 of subunit a (E. coli numbering) are involved in ion transport [43][44][45], but recent studies revealed that only Arg-210 is essential for ion conduction [46]. This residue is in close proximity to the active carboxylate of subunit c (Asp-61 in E. coli) [44,46,47], and as we shall see later, both residues are key players in ion transport.…”

Photosynthesis research in Italy: a review

“…capsulatus B100 are available (Borghese et al 1998a, b) and genetic techniques for site-specific mutagenesis have been set up (Turina and Melandri, 2002). These studies have lead to the production of a number of site-specific mutants and, for some of these, to the functional characterization of their phenotypes (Turina and Melandri 2002). [For a historical perspective on ATP Synthase, see W Junge (pp 571-595) in Govindjee et al (2005).…”