BCMB – 8110

Control of Electron Transfer in Biology1- Key Concepts

-Transfer Potentials-Electron transfer cofactors

2- Overview of the electron transport chain

-Complex I-Complex II-Complex III-Complex IV

3- Advanced Concepts in Protein Structure/Function-Mechanisms of redox control-Mechanisms of proton transfer-Mechanisms of electron transfer

Transfer Potential and the Meaning of Life

It’s all about energy!

Free Energy and Reduction Potential

Transfer Potential

Electron Carriers – Coenzyme Q

Electron Carriers – Iron Sulfur Clusters

Universal, Mobile Electron Carriers – Ferredoxins

Electron Carriers – Low Potential Ferredoxins

Electron Carriers – Rieske Type Iron Sulfur Clusters

Electron Carriers – Cytochromes

Electron Carriers – Cytochromes

Electron Carriers – Blue Copper Proteins

Electron Carriers – Flavoprotein

Electron Storage in Flavins

Complex III

Cytochrome bc1 Complex (Cont.)

Cytochrome bc1 Complex (Cont.)

Cytochrome bc1 Complex (Cont.)

Controlling Reduction Potentials, ElectronTransferAnd Proton Transfer

Rule #1, In most cases, especially for complex metallocenters, protonand electron transfer are coupled.

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Rubredoxin

Redox Control – Nitrogenase

Redox Control – Nitrogenase

Redox Control – Nitrogenase

Redox Control – Nitrogenase

Structural Models of the P-Cluster

Peters et al. Biochemistry (1997) 36 1181-1187

Redox Control – Nitrogenase

-360

-340

-320

-300

-280

-260

-240

-220

-200E

m2

(mV

)

9.08.58.07.57.06.56.05.5

pH

Slope = -53 mV / pH

pH-dependence for the P Redox Couple2+/1+

Model for P-Cluster Redox and Proton Transfer Reactions

P2+

P1+(H+)P2+(H+)

P1+ PN

PN (H+)

Em2

Em2H

Em1

Em1H

pKa pKa pKa

< -348 mV

> -224 mV

< 6.0 > 8.5 > 8.5

-310 mV

Structural Models of the P-Cluster

Peters et al. Biochemistry (1997) 36 1181-1187

e-

8 H+ + 8e- + N2

2 NH3 + H2

e-

H+

P N P 1+ P 2+pH 7.0-310 mV -260 mV

P N P 1+ P 2+

-310 mV -310 mV

pH 8.0

Cytochrome Oxidase- Proton Transfer

Coupled Proton/Electron transfer – CytochromeOxidase

Coupled Proton/Electron transfer – CytochromeOxidase

Coupled Proton/Electron transfer – CytochromeOxidase

Coupled Proton/Electron transfer – CytochromeOxidase

COX + Cyc c + broken beef heart mitochondria.

Capitanio et al. Biochemistry 42(16) p.4607-4612

Coupled Proton/Electron transfer – CytochromeOxidase

Coupled Proton/Electron transfer – CytochromeOxidase

Electron Transfer – Theory and Experiment

Electron Transfer – Theory and Experiment

Electron Transfer – Theory and Experiment

Electron Transfer – Theory and Experiment

Electron Transfer – Theory and Experiment

Electron Transfer – Theory and Experiment