RelevancePsbQ, also known as 16 kDa protein, is one of the three components (PsbO, PsbP and PsbQ) of oxygen evolving complex (OEC) in higher plants. The cyanobacterial photosystem II have five associated extrinsic proteins, PsbO, PsbP, PsbQ, PsbU and PsbV. This class of subunits is located on the lumen face of the thylakoid membranes. PsbQ has a regulatory role on the water oxidation machinery.
The lack of PsbQ in cyanobacteria affects the stability of PsbV protein; and it is likely that the major function of cyanobacterial PsbQ is to stabilize the PsbV protein, thereby contributing to the protection of the catalytic Mn(4)-Ca(1)-Cl(x) cluster of the water oxidation machinery.