Abstract
The extrinsic PsbO protein which is conserved in all of oxygen-evolving organisms plays important roles in maintaining the stability and activity of Mn cluster for the water-oxidizing reactions. We examined the binding domains of spinach and red algal PsbO responsible for electrostatic interaction with PSII intrinsic proteins by chemical modification. The results showed that Lys residues in six domains of PsbO are commonly involved in the interaction. To determine which Lys residues in the six domains directly participate in the interaction, we constructed 8 mutant PsbO proteins in which positively charged Lys residues were substituted to non-charged Gly residues by site-directed mutagenesis. The results showed that K15G, K74G and K164G largely lost its binding ability, while K127G, K198G and K241G did not. Lys residues on PsbO responsible for the electrostatic interaction with PSII intrinsic proteins will be discussed in crystal structure of PSII.
