Reconstitution of photosynthetic water-splitting activity by the addition of 33 kDa polypeptide to urea-treated PS II reaction center complex

Treatment with 3 M urea of the oxygen-evolving PS II core complex previously described [(1985) FEBS Lett. 179, 60-64] resulted in approx. 80% release of 33 kDa polypeptide accompanied by partial (40%) inactivation of the water-splitting activity. On the other hand, the treatment only slightly decreased the amount of bound Mn from 2.7 to 2.0 atoms per 50 chlorophyll a . Readdition of purified 33 kDa polypeptide to the urea-treated sample almost completely restored the oxygen-evolving activity. These results suggest that the Mn atoms functional for oxygen-evolving activity are located in the PS II reaction center core complex, and that the 33 kDa polypeptide is not essential for water oxidation but is necessary for the full oxygenevolving activity. Photosystem II Reaction center Reconstitution Urea treatment Manganese binding 33 kDa polypeptide Oxygen evolution