Association of the 33‐kDa polypeptide with the 43‐kDa component in photosystem II particles

Abstract
The organization of polypeptides and Mn atoms in the oxygen‐evolution system was studied by analyzing the effects of protease treatment on photosystem (PS) II particles from spinach chloroplasts. Hydrolysis of the 47‐ and 43‐kDa polypeptides of the PS II core complex had similar profiles of dependence on trypsin concentration in the treatment of control PS II particles and NaCl‐washed particles, which were devoid of the peripheral 24‐ and 18‐kDa polypeptides. In CaCl2‐washed particles, which were depleted of the 33‐kDa polypeptide besides the 24‐ and 18‐kDa polypeptides, the 43‐kDa polypeptide was much more sensitive to trypsin than the 47‐kDa polypeptide. Chymotrypsin treatment gave similar results. These findings suggest that the 33‐kDa polypeptide is associated to the 43‐kDa polypeptide and shields it from tryptic attack. Changes of the amount of Mn in the PS II and salt‐washed particles on protease treatment indicated a heterogeneity of binding sites of Mn in the PS II particles

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