Purification and properties of an oxygen-evolving reaction center complex from photosystem II membranes: A simple procedure utilizing a non-ionic detergent and elevated ionic strength

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 O 2/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.