PSII reaction centre components are generating the redox potential required to drive highly oxidizing water splitting reaction. Four Mn atoms are present on a lumenal surface and form the catalyctic site of the water-splitting reaction which is in close association with the 33 kDa (PsbO), 23 kDa (PsbP) and 17 kDa (PsbQ) extrinistic subunits of oxygen evolving complex OEC. A 33-kDa extrinsic protein is also termed the Mn-stabilizing protein (MSP), however recent evidences shown that it is C-terminal domain of PsbA (D1) protein which is involved in in the assembly and stabilization of the OEC.
