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Requirements for oxidative phosphorylation

Requirements for oxidative phosphorylation . Requirements for the production of ATP. 1. An ion impermeable membrane. A mechanism for moving protons (H + ) across the membrane to produce an energy-rich proton gradient. A mechanism to capture the energy made

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Requirements for oxidative phosphorylation

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  1. Requirements for oxidative phosphorylation Requirements for the production of ATP 1. An ion impermeable membrane • A mechanism for moving protons (H+) across • the membrane to produce an energy-rich • proton gradient • A mechanism to capture the energy made • available as protons move down the proton • gradient

  2. Requirements for oxidative phosphorylation 1. An ion impermeable membrane See Fig 14.6 in Horton

  3. A typical representation of an electron transport chain. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

  4. Electron transport chain 2 4 4 2H+ 4 Requirements for oxidative phosphorylation • A mechanism for moving protons (H+) across • the membrane to produce an energy-rich • proton gradient

  5. H+ H H NMN AMP nicotinamide

  6. 1 5 -H+, -e- 2H+ 2e- H -H+, -e- H FMNH2 (hydroquinone) H FMNH (semiquinone) Isoalloxazine

  7. H H FADH2

  8. + 1 e-, +2H+ + 1 e- - Semiquinone ( Q- ) H H Ubiquinol ( QH2 ) Isoprenoid unit

  9. Non-heme iron sulfur proteins (Fe-S clusters) 2S -2Fe Cys Cys S S S Fe Fe S S S Cys Cys 4S -4Fe Cys S Fe S Cys S Fe S S Fe S Fe Cys S Cys S

  10. Cytochromes • Heme-containing proteins • Classified as a, b or c based on absorption spectrum • Electron transport has: a and a3, b566 (bL) and b562 (bH). • and c and c1 • carry 1 electron per heme iron • a, a3, b566,,, b562,, and c1 are integral membrane proteins • c is a peripheral membrane protein on outer surface of • inner mitochondrial membrane

  11. proprionate methyl Heme group in cytochromes Heme group of Cytochrome b See fig. 7-34 in Horton

  12. Heme group in cytochromes a and c See fig. 7-34 in Horton

  13. ba 555-567 nm ca 550-558 nm aa 592-604 nm See Fig 7-35 -Horton

  14. b c a O2 Normal Blocked between Cyt b and c1 a and c fully oxidised b fully reduced Difference spectra = spectra of experimental– spectra of fully oxidized mito

  15. Substrate or complex Eo’ (V) NADH -0.32 Complex I FMN Fe-S clusters -0.30 -0.25 - -0.05 Succinate + 0.03 Complex II FAD Fe-S clusters 0.0 -0.26 – 0.00 QH2/Q +0.04 Complex III Fe-S clusters Cyt B560 Cyt b566 Cyt c1 +0.28 - 0.1 + 0.05 + 0.22 Cytochrome c + 0.23 Complex IV Cyt a CuA Cyt a3 CuB + 0.21 + 0.24 + 0.39 + 0.34 O2 + 0.82 Standard redox potentials of mitochondrial oxidation-reduction components

  16. Electron transport complexes Complex I: NADH-Q reductase DE0' = + 0.32 V DG = -70 kJ/2e- Contains at least 34 polypeptides FMN, 2Fe-2S and 4Fe-4S clusters, tightly bound CoQ Mr = 880kD Result: 2 e- from NADH to CoQ 4 H+ from matrix to intermembrane space NADH + H+ + CoQox NADH + CoQH2 Intermembrane space 4H+ 2H+ QH2 FMNH2 Fe-S 2e- 2e- FMN Q 4H+ matrix NAD NADH + H+

  17. QH2 2 x e- Fe-S 2 x e- Q FAD 2e- 2H+ Fumarate + 2H+ succinate Complex II: succinate dehydrogenase/ succinate – Q reductase DE0' = + 0.015 V DG = -2.9 kJ/2e- Contains: FAD, Fe_S Result: 2 e- from FADH2 to CoQ No protons translocated FADH2 + CoQox FADH + CoQH2 Intermembrane space matrix

  18. 4H+ 2H+ c Q 2 x e- QH2 2H+ Complex III: Cytochrome C reductase DE0' = + 0.25 V DG = --37 kJ/2e- Contains: Cyt b (bL and bH), Cyt c1, Fe-S protein, several additional proteins Result: 2 e- from CoQH2 to Cyt c 2 H+ taken up from matrix, 4 H+ to intermembrane space CoQH2 + 2Cyt c (Fe+3) CoQ + 2Cyt c (Fe+2) Intermembrane space matrix

  19. CoQ cycle C1 Fe-S bL bH C1 C1 Fe-S Fe-S bL bL bH bH C1 Fe-S bL bH

  20. 2H+ c Complex IV: Cytochrome oxidase DE0' = + 0.57 V DG = -110 kJ/2e- Contains: 10 subunits, Cyt a and Cyt a3, 2 Cu (A , B) Result: 4 e- from 4 Cyt c to form 2 H2O 8 H+ taken up from matrix, 4 H+ to intermembrane space 2 x e- a3 - CuB a - CuA 2 x e- 4Cyt c (Fe+2)+ 4 H+ + O2 4Cyt c (Fe+3) + 2 H2O H2O 2H+ 1/2O2 2H+ Intermembrane space matrix

  21. Cu2+ OH- OH- Fe3+ Cu+ Cu2+ Fe2+ O- Fe3+ H Cu2+ O- O- O- Cu+ O- Fe3+ Fe3+ O- Cytochrome oxidase: electron transfer to O2 CuB a3 Cu2+ . Fe3+ . See Horton, fig 14.16

  22. Electron transport chain H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ CoQ CoQ Cyt c Cyt c H+ H+ H+ Cplx IV Cplx III Cplx I e- H2O NADH + H+ H+ H+ 2H+ + ½ O2 H+ NAD Summary of protons translocated per 2 e-

  23. 1997 Nobel Prize for Chemistry Paul D. BoyerJohn E. WalkerJens C. Skou "for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP)" "for the first discovery of an ion-transporting enzyme, Na+, K+ -ATPase"

  24. ATP synthase These and the following images can be found at the home page of Boris A. Feniouk (http://www.biologie.uni-osnabrueck.de/biophysik/Feniouk/Home.html) that contains a wealth of additional information on ATP synthesis. See also Horton p 450 and 451.

  25. Binding-change mechanism (See page 451 in Horton) From: http://www.cse.ucsc.edu/~hongwang/ATP_synthase.html

  26. For movies and details go to: http://www.res.titech.ac.jp/~seibutu/

  27. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ c c Cplx IV Cplx III ATP synthase Cplx I CoQ CoQ H2O e- H+ H+ H+ NADH + H+ 2H+ + ½ O2 ATP ADP + PO4 H+ NAD

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