Abstract
The extrinsic 33 kDa protein which plays important roles in maintaining the stability and activity of Mn cluster electrostatically binds to PSII intrinsic protein. We have reported that the positive charges on the protein are important for electrostatic interaction with PSII intrinsic proteins by chemical modification of charged amino acids, and estimated that Lys residues in six domains of the 33 kDa protein are commonly involved in the binding in both spinach and red algal PSIIs. In this study, we examined which Lys residues in the six domains directly participate in the interaction by site-directed mutagenesis. The 33 kDa protein substituted 15Lys and 164Lys to Gly could not functionally bind to PSII, while the protein substituted 198Lys to Gly functionally bound. On the basis of these results, we will discuss Lys residues on the 33 kDa protein responsible for the electrostatic interaction with PSII intrinsic proteins.
