Porphyra Yezoensis Photosystem ¢ò Protein Complex Structural And Functional Changes In The Ontogeny

Jun Liang (Experimental marine biology)Directed by Guohong Peng The life cycle of red algae,Porphyra yezoensis consists of two phases:sporophyte and gametophyte.The structure and function of photosystems which are purified from the different life cycle of Porphyra yezoensis are compared.To obtain the active thylakoid membranes of sporophyte and gametophyte,three different buffers are used: 20mM Mes-Na(pH6.4),30mM Naphosphate buffer(pH7.0), 50mM Hepes buffer(pH7.8)。According to the results of photosysthetic rate the best buffer is 30mM Naphosphate buffer(pH7.0).The thylakoid membrane proteins are solubilized withdifferent detergents and the most active thylakoid membrane proteins are gotten by 3%LM.The 3%LM-solubilized fractions are separated by different methods: sucrose density gradient ultracentrifugation,anion exchange column,molecular size elution column.The best method is to separate the 3%LM-solubilized fractions by sucrose density gradient ultracentrifugation and futher purified by Superdex 200 molecular size elution column. For the first time we purify the PSII complexes from different life cycle of Porphyra yezoensis.The activities of the purified PSII complexes show that the activities of PSII complexes of sporophyte:2216.4μmolO2/chl(mg).h are higher than that of gametophyte:2161.6μmolO2/chl(mg).h.The polypeptide components of purified photosystem II complexes are investigated by SDS-PAGE and the results show that sporophyte contains more low-molecular-mass polypeptide components between 10KDa and 25KDa than gametophyte. The amino acid sequences of some protein bands from the SDS-PAGE are measured and the results show that PSII complexes purified from sporophyte contains PS II P680 chlorophyll a apoprotein CP-47, PSII P680 chlorophyll a apoprotein CP-43 and PSII reaction center protein D2, gametophyte PSII complexes contain PS II P680 chlorophyll a apoprotein CP-47 and PSII reaction center protein D1.