THE ROLE OF CP-47 IN THE EVOLUTION OF OXYGEN AND THE BINDING OF THE EXTRINSIC 33-KDA PROTEIN TO THE CORE COMPLEX OF PHOTOSYSTEM-II AS DETERMINED BY LIMITED PROTEOLYSIS

In order to identify the domain within Photosystem II complexes that f unctions in the evolution of oxygen, we performed limited proteolysis with lysylendopeptidase of the core complex of Photosystem II which ha d been depleted of the extrinsic 33-kDa protein (Mn-stabilizing protei n). The cleavage sites were estimated from the amino-terminal sequence s of the degradation fragments, their apparent molecular masses and am ino-acid compositions. Under certain conditions, the D2 protein was cl eaved at Lys13; and a chlorophyll a-binding protein, CP47, was cleaved at Lys227 and Lys389. Another chlorophyll a-binding protein, CP43, wa s degraded more rapidly than CP47. The oxygen-evolving activity,and th e capacity for rebinding of the 33-kDa protein to the core complex of Photosystem II decreased in parallel, with kinetics very similar to th ose of the cleavage of CP47 at Lys389. These observations strongly sug gest that the hydrophilic domain around Lys389 of CP 47, which are loc ated on the lumenal side, is important in the binding of the 33-kDa pr otein and in maintaining the oxygen-evolving activity of the Photosyst em II complex.