Extraction and characterization of oxygen-evolving Photosystem II complexes from a thermophilic cyanobacterium Synechococcus spec.

Photomembranes from a thermophilic cyanobacterium Synechococcus spec, were treated with zwitterionic detergents of the type C n H 2 n +1 N + (CH 3 ) 2 -(CH 2 ) 3 SO 3 , with n = 8,10,12,14,16. PS II complexes most active in oxygen evolution could be extracted with detergent containing either a decyl ( n = 10) or a dodecyl ( n = 12) chain. It was shown that up to 95% of all PS II present in the membranes could be extracted without loss of water oxidizing ability. Only minor parts of PS I were solubilized by this treatment. In the extracted PS II complex the ratio of active reaction centers is PS II/PS I = 20. The PS II complex contains the antennae pigments allophycocyanin (APC) and chlorophyll a relative to the reaction center Chl a 11 ( P -680) according to Chl a 11 /Chl a /APC = 1:100:33. Polypeptide separation showed that proteins with apparent molecular masses of 110 kDa, 95 kDa and 48 kDa are most prominently accumulated in the extract.