Effect of Trypsin Treatment of Photosystem I Particles on the Electron Donation to P700

Abstract

Proteolysis of photosystem I particles had no effect on P700 oxidation but did inhibit the rate of P700⁺ reduction. The V_max values were decreased for both dichlorophenol and plastocyanin, but the K_m values were unaffected indicating that trypsin treatment altered electron transfer rather than the binding of the donor to the photosystem I complex. The salt dependence of P700⁺ reduction was unaffected. The effects of P700⁺ reduction were the same for the preparations of different workers (Shiozawa, Alberte, Thornber 1974 Arch Biochem Biophys 165: 388; and Bengis, Nelson 1975 J Biol Chem 250: 2783).