Purification and properties of an oxygen‐evolving reaction center complex from photosystem II membranes

A method is reported for the isolation of a highly resolved oxygen‐evolving photosystem II reaction center preparation. This preparation can be separated from the more complex photosystem II membranes isolated by the procedure of Berthold et al. [(1981) FEBS Lett. 134, 231‐234] by use of octylglucopyranoside at elevated ionic strengths; the oxygen‐evolving material can be collected by centrifugation at relatively low g values (40000 × g) in yields estimated to be more than 80%. This new preparation lacks the 17 and 23 kDa extrinsic polypeptides; addition of calcium and chloride produces activities approaching 1000 μmol O2/h per mg chlorophyll. Although activity is maximal in the presence of 2,5‐dichloro‐β‐benzoquinone, the response of activity to ferricyanide and 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea indicates that the reducing side of photosystem II has been modified in this new oxygen‐evolving reaction center preparation.