Characterization of an Oxygen-Evolving Photosystem II Complex from a Thermophilic Cyanobacterium Synechococcus Sp.

Abstract

Photomembranes from a thermophilic cyanobacterium Synechococcus spec. were treated with zwitterionic detergents of the type CnH2n+1N+(CH3)2-(CH2)3-SO3-, with n = 8,10,12,14,16. PS II complexes most active in oxygen evolution could be extrated with detergent containing either a dexyl (n= 10) or a dodecyl (n= 12) chain. It was shown that up to 95% of all PSII present in the membranes could be extrated without loss of water oxidizing ability. Only minor parts of PS I were solubilized by this treatment. In the extracted PS II complex the ration of active reaction centers is PS II/PS I = 20. The PS II complex contains the antennae pigments allophycocyanin (APC) anc chlorophyll a relative to the reaction center Chl aII (P-680) according to Chl aII/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.