Isolation and characterization of a photosystem II core complex depleted in the 43 kDa-chlorophyll-binding subunit

The photosystem II core complex purified from digitonin extracts of spinach chloroplasts was resolved into two chlorophyll-protein complexes by digitonin polyacrylamide gel electrophoresis after treatment with 1 M potassium thiocyanate. One of the chlorophyll-protein complexes resolved consisted of 47, 32, 30 and 9 kDa polypeptides and the other was complementally composed of only the 43 kDa polypeptide. The former complex was highly active in the photoreduction of 2, 6-dichlorophenol indophenol by 1,5-diphenylcarbazide and retained all of the components responsible for the electron transport from the secondary electron donor (Z) to the primary electron acceptor (Q_A). EPR signal II_fast and II_slow were also preserved in this complex although their hyperfine structures were largely modified. The complex was estimated to contain 1.8 molecules of plastoquinone A as well as 1.5, 3.7 and 3.9 molecules of cytochrome b559, pheophytin α and β-carotene, respectively, per Q_A. These results indicate that potassium thiocyanate specifically removes the 43 kDa polypeptide from the PS II core complex leaving the electron transport system in an almost intact state. Copyring