Cytoch Intermembrane Rieske iron-sulfur protein space(P side Cytochrome b Cytochrome c Iron Cytochrome c1, sulfur protein oboe Intermembrane Matrix space(P side) (N side) 2Fe-2S center H Cytochrome boohoo Matrix (N side) The three core subunits Cytochrome bc, complex (complex Im)
Cytochrome bc1 complex (complex III) The three core subunits
Oxidation of first QH2 Electron path Oxidation of second QH2 in complex Ill Intermembrane (P side) 2H 2H C Cvt The Th QH bH y 2H Matrix (N side The Ist QH2 The 2nd QH2 QH2+ Cyt cr( oxidized)→→ QH2+Q+2HN+ Cyt c,(oxidized) Q+ 2Hp Cyt c,(reduced) QH2+ 2Hp +Q+ Cyt c1(reduced) QH2+ 2 Cyt c,(oxidized)+ 2HN -Q+2 Cyt cn(reduced)+ 4Hp
Electron path in complex III The Q cycle The Q cycle The 1st QH2 The 2nd QH2
6. Electrons of Cyt c are transferred to O2 on cytochrome oxidase (complex Iv) A 204 KD 13-subunit protein complex, with structure determined in 1996 Three subunits are probably critical to the function Three copper ions(2 CuA, ICuB), two heme A groups(a and a3) act as electron carriers in complex Four electrons need to be transferred to reduce one O2 molecule at the Fe-CuB center(via peroxy intermediates) of complex Iv to form 2 H2O
6. Electrons of Cyt c are transferred to O2 on cytochrome oxidase (complex IV) • A 204 kD 13-subunit protein complex, with structure determined in 1996. • Three subunits are probably critical to the function. • Three copper ions (2 CuA, 1CuB ), two heme A groups (a and a3 ) act as electron carriers in complex IV. • Four electrons need to be transferred to reduce one O2 molecule at the “Fe-CuB center” (via peroxy intermediates) of complex IV to form 2 H2O
Four substrate, protons are consumed from the n side for every four electrons transferred to one o molecule One proton is pumped out from the n to P side for each electron to be transferred by an yet defined mechanism
• Four “substrate” protons are consumed from the N side for every four electrons transferred to one O2 molecule. • One proton is pumped out from the N to P side for each electron to be transferred by an yet defined mechanism
cUa 671 Cu B Heme a Heme a The three critical subunits of cytochrome oxidase (complex IV
The three critical subunits of cytochrome oxidase (complex IV) 2CuA CuB Heme a Heme a3 CuA CuA