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Mechanism of Inhibition of Cytochrome c Oxidase by Triton X-100статья
- Авторы: Oleynikov Ilya P., Azarkina Natalia V., Vygodina Tatiana V., Konstantinov Alexander A.
- Журнал: Biochemistry (Moscow)
- Том: 86
- Номер: 1
- Год издания: 2021
- Издательство: Pleiades Publishing, Ltd
- Местоположение издательства: Road Town, United Kingdom
- Первая страница: 44
- Последняя страница: 58
- DOI: 10.1134/s0006297921010053
- Аннотация: It is known that Triton X100 (TX) reversibly inhibits activity of cytochrome c oxidase (CcO). The mechanism ofinhibition is analyzed in this work. The action of TX is not directed to the reaction of CcO with cytochrome c, does not causetransition of the enzyme to the “slow” form, and is not associated with monomerization of the enzyme complex. TX completely suppresses oxygen reduction by CcO, but inhibition is prevented and partially reversed by dodecylβ−Dmaltoside(DDM), a detergent used to maintain CcO in solution. A 1/1 stoichiometry competition is shown between DDM and TXfor binding to CcO, with Ki = 0.3 mM and affinity of DDM for the enzyme of 1.2 mM. TX interaction with the oxidizedenzyme induces spectral response with maximum at 421 nm and [TX]1/2 = 0.28 mM, presumably associated with heme a3.When CcO interacts with excess of H2O2 TX affects equilibrium of the oxygen intermediates of the catalytic center accelerating the FI607 → FII580 transition, inhibits generation of O2•− by the enzyme, and, to a lesser extent, suppresses the catalase partial activity. The observed effects can be explained by inhibition of the conversion of the intermediate FII580 to thefree oxidized state during the catalytic cycle. TX suppresses intraprotein electron transfer between hemes a and a3 duringenzyme turnover. Partial peroxidase activity of CcO remains relatively resistant to TX under conditions that block oxidasereaction effectively. These features indicate an impairment of the K proton channel conductivity. We suggest that TX interacts with CcO at the Bile Acid Binding Site (BABS) that is located on the subunit I at the Kchannel mouth and contactswith amphipathic regulators of CcO [Buhrow et al. (2013) Biochemistry, 52, 69957006]. Apparently, TX mimics the physiological ligand of BABS, whereas the DDM molecule mimics an endogenous phospholipid bound at the edge of BABS thatcontrols effective affinity for the ligand.
- Добавил в систему: Лапашина Анна Сергеевна