Journal
FEBS LETTERS
Volume 597, Issue 2, Pages 237-245Publisher
WILEY
DOI: 10.1002/1873-3468.14518
Keywords
coupled electron-proton transfer; Mitochondria; NADH dehydrogenase; proton pumping; proton translocation; respiratory complex I
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Using quantum chemistry and electrostatic calculations, the pKa of the reduced quinone in the catalytic cavity of complex I is found to be very high, indicating that a single protonation reaction can drive four protons across the membrane. Based on these calculations, a possible scheme of redox-linked proton pumping by complex I is proposed.
Complex I is a key proton-pumping enzyme in bacterial and mitochondrial respiratory electron transport chains. Using quantum chemistry and electrostatic calculations, we have examined the pKa of the reduced quinone QH-/QH2 in the catalytic cavity of complex I. We find that pKa (QH-/QH2) is very high, above 20. This means that the energy of a single protonation reaction of the doubly reduced quinone (i.e. the reduced semiquinone QH-) is sufficient to drive four protons across the membrane with a potential of 180 mV. Based on these calculations, we propose a possible scheme of redox-linked proton pumping by complex I. The model explains how the energy of the protonation reaction can be divided equally among four pumping units of the pump, and how a single proton can drive translocation of four additional protons in multiple pumping blocks.
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