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 functions in the evolution of oxygen, we performed limited proteolysis with lysylendopeptidase of the core complex of Photosystem II which had been depleted of the extrinsic 33-kDa protein (Mn-stabilizing protein). The cleavage sites were estimated from the amino-terminal sequences of the degradation fragments, their apparent molecular masses and amino-acid compositions. Under certain conditions, the D2 protein was cleaved at Lys13; and a chlorophyll a-binding protein, CP47, was cleaved at Lys227 and Lys389. Another chlorophyll a-binding protein, CP43, was degraded more rapidly than CP47. The oxygen-evolving activity,and the capacity for rebinding of the 33-kDa protein to the core complex of Photosystem II decreased in parallel, with kinetics very similar to those of the cleavage of CP47 at Lys389. These observations strongly suggest that the hydrophilic domain around Lys389 of CP 47, which are located on the lumenal side, is important in the binding of the 33-kDa protein and in maintaining the oxygen-evolving activity of the Photosystem II complex.