ミトコンドリアにおけるATP合成のモデル反応

概要

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Mitochondrial F1-F0 complex catalyzes ATP synthesis coupled with proton translocation down the electrochemical potential gradient (ΔμH+) across the inner membrane. F1, the catalytic sector of the complex, can be detached from the membrane to be a soluble protein. Recently, we found that soluble F1 catalyzed ATP synthesis from medium ADP and Pi in the presence of dimethylsulfoxide (DMSO). This finding indicates that energy input of ΔμH+ is not essential to covalent binding of ADP and Pi to form ATP on F1. The synthesized ATP was bound to F1 to compose F1-ATP complex, suggesting that the energy input is necessary for the release of ATP from F1. The F1-ATP complex seemed to be formed also in the absence of DMSO. DMSO increased the affinity of F1 for Pi and shifted the equilibrium between F1-ATP complex and F1-ADP-Pi complex. Since it is the most simple ATP-synthesizing system ever known, it might be utilized to solve other problems about the mechanism of ATP synthesis. F1 has two types of nucleotide-binding sites, tight binding sites and exchangeble binding sites. However, it has not been exclusively determined which is the catalytic site of ATP synthesis. We found that ATP was formed by soluble F1 from ADP bound to the exchangeable binding site (s) but not from that bound to the tight binding sites.
日本生物物理学会の論文