Mutagenesis of Ligands to the Cofactors in Photosystem I
The electron transfer chain of Photosystem I (PS I) is made up of six chlorophylls (P700, A, and A0), two quinones (A1), and three iron–sulfur centers (FXX, FA, and FB). The chlorophylls and quinones formtwo potential pathways for electron transfer from P700 to FX. The electron transfer chain chlorophylls are also excitonically coupled as indicated by the spectrally broad transient bleaching observed between 660 and 700 nm upon initial excitation. This article reviews how specific mutagenesis of the ligands of each cofactor is being used to address some of the outstanding questions raised by the structural model of Photosystem I.
KeywordsElectron Transfer Electron Paramagnetic Resonance Axial Ligand Primary Charge Separation Sulfur Center
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