Extrinsic conditions influence the self-association and structure of IF ₁ , the regulatory protein of mitochondrial ATP synthase

Abstract

The endogenous inhibitor of ATP synthase in mitochondria, called IF 1 , conserves cellular energy when the proton-motive force collapses by inhibiting ATP hydrolysis. Around neutrality, the 84-amino-acid bovine IF 1 is thought to self-assemble into active dimers and, under alkaline conditions, into inactive tetramers and higher oligomers. Dimerization is mediated by formation of an antiparallel α-helical coiled-coil involving residues 44-84. The inhibitory region of each monomer from residues 1-46 is largely α-helical in crystals, but disordered in solution. The formation of the inhibited enzyme complex requires the hydrolysis of two ATP molecules, and in the complex the disordered region from residues 8-13 is extended and is followed by an α-helix from residues 14-18 and a longer α-helix from residue 21, which continues unbroken into the coiled-coil region. From residues 21-46, the long α-helix binds to other α-helices in the C-terminal region of predominantly one of the β-subunits in the most closed of the three catalytic interfaces. The definition of the factors that influence the self-association of IF 1 is a key to understanding the regulation of its inhibitory properties. Therefore, we investigated the influence of pH and salt-types on the self-association of bovine IF 1 and the folding of its unfolded region. We identified the equilibrium between dimers and tetramers as a potential central factor in the in vivo modulation of the inhibitory activity and suggest that the intrinsically disordered region makes its inhibitory potency exquisitely sensitive and responsive to physiological changes that influence the capability of mitochondria to make ATP. mitochondria | ATP hydrolysis | regulation | inhibitor | intrinsically disordered protein

ATP Synthase Subunit Epsilon Overexpression Promotes Metastasis by Modulating AMPK Signaling to Induce Epithelial-to-Mesenchymal Transition and Is a Poor Prognostic Marker in Colorectal Cancer Patients

“…However, extrinsic conditions influence (pH, ion concentration, etc.) the self-association and structure of IF1 [42]. In further experimental design, we will evaluate the mitochondrial membrane potential (△ Ψm) and identify the detailed interplay between ATP5E and ATPIF1.…”

NH‐sulfoximine: A novel pharmacological inhibitor of the mitochondrial F1Fo‐ATPase, which suppresses viability of cancerous cells

“…Data are shown as mean values ± SEM (n = 5). *P < 0.05, significantly different as indicated F 1 F o -ATPase into an inhibited state (Boreikaite, Wicky, Watt, Clarke, & Walker, 2019;Faccenda & Campanella, 2012;Rouslin & Broge, 1996).…”

“…Over the years, the interest in such selective regulation of the F 1 F o ‐ATPsynthase has concentrated our attention on the physiology and pharmacology of IF 1 , a protein that, in response to the inhibition of respiration, prevents the consumption of ATP by forcing the F 1 F o ‐ATPase into an inhibited state (Boreikaite, Wicky, Watt, Clarke, & Walker, 2019; Faccenda & Campanella, 2012; Rouslin & Broge, 1996). In addition to the work generated following genetic modulation of IF 1 , we characterized a chemical compound, BTB, which selectively limits ATP consumption by the F 1 F o ‐ATPsynthase by increasing the activation of IF 1 .…”

Mitochondrial F1FOATP synthase determines the local proton motive force in cristae tips

“…Under glycolytic, but not OXPHOS conditions, IF1-H49K had a positive effect on ATP production rates. We conclude that the endogenous IF1 was not fully active under glycolytic conditions, likely because the matrix pH was basic (pH>7.5) and IF1 is activated at pH<7.5 (Boreikaite et al, 2019;Zanotti et al, 2009). The pH-independently active IF1 (IF1-H49K) obviously blocked ATPase more efficiently.…”