Functional Structure of the Oxygen-Evolving Unit of Photosystem II as Determined by Radiation Inactivation

概要

論文の詳細を見る
The size of the complex that is essential for the electron-transfer activity from the oxygen-evolving center to the secondary electron acceptor, Q_B, is about 250 kDa, as determined by target-size analysis after the radiation inactivation of functions of photosystem II (PS II). Inter-Chl tranfer of excitation energy was insensitive to the radiation inactivation indicating that the masses of CP47, CP43, and light-harvesting Chl a/b proteins are not included in the functional size of the oxygen-evolving PS II complex. The transfer of electrons from the secondary electron donor, Z, to Q_B was catalyzed by a unit of only 65 kDa. The sizes of the complexes involved in these light-induced functions of PS II were dependent on the intensity of actinic light. Under saturating intensities of light, the functional size of the complex for transfer of electrons from Z to Q_B Was 38 kDa, with a corresponding decrease in the size of the oxygen-evolving PS II from 250 kDa to 125 kDa [Takahashi, Mano and Asada (1985) Plant Cell Physiol. 26: 383]. The protein of about 30 kDa functions in the photoreduction of the pheophytin molecule, as well as in the electron transfer from Z to Q_A. Under low-intensity light, complexes having the same sizes as those of the basal functional complexes under saturating-intensity light are further required, probably to stabilize separated charges in the PS II reaction center and the oxygen-evolving center.
日本植物生理学会の論文