C‐terminal regulatory domain of the ε subunit of F_oF₁ ATP synthase enhances the ATP‐dependent H⁺ pumping that is involved in the maintenance of cellular membrane potential in Bacillus subtilis

Abstract

The ε subunit of FoF1‐ATPase/synthase (FoF1) plays a crucial role in regulating FoF1 activity. To understand the physiological significance of the ε subunit‐mediated regulation of FoF1 in Bacillus subtilis, we constructed and characterized a mutant harboring a deletion in the C‐terminal regulatory domain of the ε subunit (ε∆C). Analyses using inverted membrane vesicles revealed that the ε∆C mutation decreased ATPase activity and the ATP‐dependent H+‐pumping activity of FoF1. To enhance the effects of ε∆C mutation, this mutation was introduced into a ∆rrn8 strain harboring only two of the 10 rrn (rRNA) operons (∆rrn8 ε∆C mutant strain). Interestingly, growth of the ∆rrn8 ε∆C mutant stalled at late‐exponential phase. During the stalled growth phase, the membrane potential of the ∆rrn8 ε∆C mutant cells was significantly reduced, which led to a decrease in the cellular level of 70S ribosomes. The growth stalling was suppressed by adding glucose into the culture medium. Our findings suggest that the C‐terminal region of the ε subunit is important for alleviating the temporal reduction in the membrane potential, by enhancing the ATP‐dependent H+‐pumping activity of FoF1.

Evolution of the Inhibitory and Non-Inhibitory ε, ζ, and IF1 Subunits of the F1FO-ATPase as Related to the Endosymbiotic Origin of Mitochondria

“…This seems to take place because the Bs-ε is somehow relieving the intrinsic kinetic MgADP inhibition [53]. This Bs-ε activating effect has also been demonstrated in the full BsF1FO-ATPase [54]. Furthermore, it has also been shown that the last five residues of the very C-terminus of the ε subunit of the F-ATP synthase from E. coli (Ec-ε) enhance the clockwise F-ATP synthase turnover and the respiratory E. coli growth.…”

<p>Pump Proton and Laryngeal H⁺/K⁺ ATPases</p>

“… 9 , 21 This is the mechanism targeted by PPI therapy. 7 , 8 , 16 H + /K + ATPases contain the catalytic α-subunit and non-catalytic glycosylation β-subunit. The α-subunit of the H + /K + ATPases of different species is made up of 1035 amino acids and includes the catalytic center, which resides in the large cytoplasmic domain of the enzyme.…”

“…9 As a byproduct of the pump activity, a pH gradient forms on either side of the membrane. Four types of proton pumps with ATPase activity have been recognized: P-type, [10][11][12][13][14] F-type, [15][16][17] V-type, [18][19][20] and ABC ATPases. 18…”

Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins

“…The ATP-driven H + pump activity of CF o CF 1 in the thylakoid membranes was measured according to the fluorescence quenching of ACMA based on a previous method with some modifications ( 36 , 55 ). The emitted fluorescence of ACMA (excitation at 410 nm, emission at 480 nm) was measured using a FP-8500 spectrofluorometer (Jasco), in which the temperature in the sample chamber was 25 °C.…”