Isolation and characterization of PSII core complexes from a brown alga, Laminaria saccharina

PSII-enriched particles, active for DCIP-reduction, were prepared from Laminaria saccharina chloroplasts, and PSII core complexes were further purified by ion-exchange chromatography. They contained several polypeptides, four of them cross-reacting with antibodies raised against CP47, CP43, D1 and D2 of green plants. A second chromatography was required to separate: (i) a core antenna, composed of 51 kDa polypeptide subunits, binding 11 beta-carotene, 4 chlorophyll (Chl) c and 7 fucoxanthin for 100 Chl a, and reacting with CP47 antibodies; and (ii) a reaction center complex consisting of two main polypeptides of 34 and 36 kDa. The pigment stoichiometry was of 5 Chl a and 0.5 beta-carotene for 2 pheophytin a. The 34 and 36 kDa components cross-reacted with anti-D1 and anti-D2 antibodies, respectively. The presence of cytochrome b-559 was substantiated by spectrophotometry.