Pigment composition of PS II pigment protein complexes purified by anion exchange chromatography. Identification of xanthophyll cycle pigment binding proteins

The pigment composition of the chlorophyll binding proteins of Photosystem II (PS II) of spinach (Spinacea oleracea L.) has been determined using sucrose gradient ultracentrifugation, anion exchange chromatography and HPLC based pigment analysis. The xanthophyll cycle pigments violaxanthin, antheraxanthin and zeaxanthin were exclusively found in the proteins of the outer PS II antenna, with the highest amounts being present in the minor chlorophyll a/b binding proteins CP 29 and CP 26. PS II core particles containing the reaction centre proteins DI, D2, cytochrome b(559) and the proteins of the inner antenna CP 47 and CP 43 bind beta-carotene as the only carotenoid. The presence of the xanthophyll cycle pigments in the PS II antenna proteins gives further indication to their proposed role in the dissipation of excess excitation energy. The purification procedure presented in this study differs from previous isolation methods (i. e. isoelectric focusing) used to determine the pigment composition of the PS II proteins. The pigment stoichiometries shown here therefore provide further insight in the pigmentation of the PS II chlorophyll binding complexes.