No abstract

The recovery of 02 evolution of cholate-treated thylakoids induced by the simultaneous addition of the 17-and 23-kDa proteins was enhanced by the further addition of thylakoid total lipids up to about 75% of the non-depleted original broken thylakoids at the optimal concentration of the lipids, through reactivation of electron transfer between the sites of DPC donation and DCIP acceptance. Novel findings clarifing the cause of the discrepancies, with regard to the requirement for the 17-kDa protein on the 02 evolution of thylakoid membranes, were also provided, i.e., when the assay of 02 evolution for the reconstituted systems was carried out at a low level of NaCl (e.g., 0.1 mM), besides the 23-kDa protein, the 17-kDa protein was also required for 02 evolution, however, at a higher level of NaCl (>5 mM) the 17-kDa protein was not. The results suggest that the 17-kDa protein takes the place of Cl-or acts as a constituent protecting Cl-in the Cl-activating sites against fluctuation of the Cl-level in the inner compartment of thylakoid membranes. Photosystem II 02 evolution Reconstitution I7-kDa proteinClThylakoid Iipid

No abstract

The reconstitution of high 0, evolution in CaCl,-treated PS II particles was achieved by the simultaneous addition of the 17-, 23-and 34kDa proteins and total thylakoid lipids in the presence of 25% glycerol and 15 mM sodium cholate. The activity of the reconstituted membranes recovered to 85% of that of the nondepleted original PS II particles at the optimal condition. By means of this reconstitution method, evidence for the cooperation of the three proteins in the recovery of 0, evolution in the CaCl,-treated PS II particles was found by changing the concentration of NaCl in the assay medium, and the relationship between the amount of manganese retained in the water-splitting complex and the 0, evolving activity was examined by using the partially solubilized PS II particles with n-octyl-/I-D-glucoside.

Repeated extractions of spinach thylakoid membranes with a solution containing 50 mM sodium cholate, 1 M NaCI, 3 mM MgClz, 0.2 M sucrose and 20 mM tricine at pH 8.4 for 15 min perfectly inhibited the 02 evolution of the thylakoids, concomitant with a complete release of the 17-and 23-kDa proteins and partial release of many other proteins from the thylakoid membranes. Recovery of 02 evolution in the cholate-treated thylakoids was achieved up to about 40% of that in the original thylakoids by the simultaneous reinsertion of the 17-and 23-kDa proteins, but not by the reinsertion of one of them only. The recovery of 02 evolution induced by the reinsertion of the 17-and 23-kDa proteins was enhanced by the further addition of a certain fraction of the crude thylakoid extract up to about 70% of the nondepleted control, suggesting that in addition to the 17-and 23-kDa proteins, one or more unknown component(s) released partially from the thylakoids upon cholate treatment is (are) also (a) constituent(s) of the 02 evolving apparatus. The purified 34-kDa protein did not replace the unknown component.