CH3 CH=CH2 CH3 CHCH3 CH2=CH CHs CHaCH CH3 N-Fe-N F CH CH2 CH2CO0 CH3 CH, CH2COO CHa CH2 CH2COO CH CH2 CH2COO Iron protoporphyrin IX Heme C (in b-type cytochromes (in c-type cytochromes) CHs CH=CHa Heme groups OH Of cytochromes CH A CH2-CH N CH3 CH3 CH3 CHs N-Fe-N CHs CHCHCOO CHO CH2CH2COO Heme A (in a-type cytochromes)
Heme groups of cytochrome proteins Heme groups Of cytochromes
2Fe-2S 4Fe-4S S-C Cys -S-F C Fe S-Cys ys (a) ferredoxin Different types of iron-sulfur centers .Iron atoms cycle between Fe2+ (reduced) and Fe3t(oxidized
Different types of iron-sulfur centers •Iron atoms cycle between Fe2+ (reduced) and Fe3+(oxidized). 2Fe-2S 4Fe-4S A ferredoxin
100 Reduced Reduced cytochromes rt c has three absorption Oxidized bands in the visible cyt c Cyt a:-600 nm; wavelengths 品9 50 Cyt b:560 nm; Cvt c:550 nm 300 400 500 600 Wavelength (nm) figure 19-4 Absorption spectra of cytochrome c in its oxidized(red) and reduced(blue)forms. Also labeled are the character- istic a, B, and y bands of the reduced form
Reduced cytochromes has three absorption bands in the visible Cyt a: ~600 nm; wavelengths Cyt b: ~560 nm; Cyt c: ~550 nm
3. NADH enters the chain at Nadh dehydrogenase(complex D) Also named as nadh:ubiquinone oxidoreductase or NADH-Q reductase a"L Shaped 850 kD multimeric protein complex of 42 different subunits (larger than a ribosome! Polypeptides encoded by both genomes fMN Fe-S centers act as prosthetic groups Exergonic electron transferring is coupled to endergonic proton pumping( with 4 Ht pumped from the matrix side to intermembrane space per electron pair transferred), with mechanism unknown Final electron acceptor is ubiquinone(coenzyme Q)
3. NADH enters the chain at NADH dehydrogenase (complex I) • Also named as NADH:ubiquinone oxidoreductase or NADH-Q reductase. • A “L” shaped 850 kD multimeric protein complex of 42 different subunits (larger than a ribosome!). • Polypeptides encoded by both genomes. • FMN, Fe-S centers act as prosthetic groups. • Exergonic electron transferring is coupled to endergonic proton pumping ( with 4 H+ pumped from the matrix side to intermembrane space per electron pair transferred), with mechanism unknown. • Final electron acceptor is ubiquinone (coenzyme Q)
4H+ Complex I Intermembrane space(P side 少N-2 tQH2 Fe-S Matrix FMN Matrix (N side) arm 2e 2H+ NADH Dehydrogenase NADH NAD (complex D)
NADH Dehydrogenase (complex I)