The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, CB2 0XY Cambridge, United Kingdom.
The Department of Chemistry, University of Cambridge, CB2 1EW Cambridge, United Kingdom.
Proc Natl Acad Sci U S A. 2019 May 21;116(21):10354-10359. doi: 10.1073/pnas.1903535116. Epub 2019 May 7.
The endogenous inhibitor of ATP synthase in mitochondria, called IF, conserves cellular energy when the proton-motive force collapses by inhibiting ATP hydrolysis. Around neutrality, the 84-amino-acid bovine IF 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 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 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.
线粒体中 ATP 合酶的内源性抑制剂，称为 IF，在质子动力崩溃时通过抑制 ATP 水解来保存细胞能量。在中性条件下，认为 84 个氨基酸的牛 IF 自我组装成活性二聚体，在碱性条件下，组装成无活性的四聚体和更高的寡聚体。二聚化是通过形成涉及残基 44-84 的反平行 α-螺旋卷曲螺旋来介导的。每个单体的抑制区来自残基 1-46 的大部分是α-螺旋在晶体中，但在溶液中是无序的。抑制酶复合物的形成需要两个 ATP 分子的水解，在复合物中，来自残基 8-13 的无序区被延伸，并被来自残基 14-18 的α-螺旋和来自残基 21 的更长的α-螺旋所跟随，该螺旋一直延伸到卷曲螺旋区域。来自残基 21-46 的长α-螺旋与主要在三个催化界面之一的β亚基的 C 末端区域的其他α-螺旋结合。影响 IF 自我结合的因素的定义是理解其抑制特性调节的关键。因此，我们研究了 pH 值和盐类对牛 IF 自我结合和其展开区折叠的影响。我们确定了二聚体和四聚体之间的平衡作为体内调节抑制活性的潜在中心因素，并表明无规卷曲区域使其抑制效力对影响线粒体产生 ATP 能力的生理变化极其敏感和响应。
