PsbO, the manganese-stabilizing protein: Analysis of the structure–function relations that provide insights into its role in photosystem II

The minireview presented here summarizes current information on the structure and function of PsbO, the photosystem II (PSII) manganese-stabilizing protein, with an emphasis on the protein’s assembly into PSII, and its function in facilitating rapid turnovers of the oxygen evolving reaction. Two putative mechanisms for functional assembly of PsbO, which behaves as an intrinsically disordered polypeptide in solution, into PSII are proposed. Finally, a model is presented for the role of PsbO in relation to the function of the Mn, Ca2+, and Cl− cofactors that are required for water oxidation, as well as for the action of hydroxide and small Mn reductants that inhibit the function of the active site of the oxygen-evolving complex.