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 Photosy stem II (PS II) of spinach (Spinacea oleracea L.) has been determined using sucrose gradient ultracentrifugation, anion exchange chromatogra phy and HPLC based pigment analysis. The xanthophyll cycle pigments vi olaxanthin, antheraxanthin and zeaxanthin were exclusively found in th e 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 4 3 bind beta-carotene as the only carotenoid. The presence of the xanth ophyll cycle pigments in the PS II antenna proteins gives further indi cation to their proposed role in the dissipation of excess excitation energy. The purification procedure presented in this study differs fro m previous isolation methods (i. e. isoelectric focusing) used to dete rmine the pigment composition of the PS II proteins. The pigment stoic hiometries shown here therefore provide further insight in the pigment ation of the PS II chlorophyll binding complexes.