Isolation, Characterization And Structural Investigation Of The Phycocyanin-chlorophyll-protein Complexes Of Chroomonas Placoidea

The cultural conditions of Chroomonas placiodea and the preparation of thylakoid membrane in laboratory are investigated in this paper; The conditions of solubilization and methods of separation by sucrose gradient centrifugation of pigment-protein complexes were established and optimized, four active pigment -protein complexes were obtained, containing two light-harvest complexes, PSI and PSII pellets respectively; Moreover, light-harvesting complexes and PSⅡpellets were resolved by TritonX-100 and separated by the second step of gradient centrifugation and IEF electrophoresis, five more sub-complexes were obtained. The complexes and sub-complexes obtained were investigated by determination of absorption spectra, fluorescence spectra, photooxidative activity determination, polypeptide and isoelectric point analysis.The results show two light-harvest complexes were small outer light-harvesting complexes(20,24KD were dominant polypeptides) and big pelltes (isoelectric point within pH5.3~5.8,mainly contain 19,24,28,37,42,70KD polypeptides) contained inner and outer antenna light-harvest complexes. PSⅡpellets were composed by two sub-complexes, PSⅡcore complexes(isoelectric point were pH5.9, 24KD were dominant polypeptides) and inner antenna complexes(isoelectric point were pH6.4, mainly contain 56,37,30,20,16 KD polypeptides). By the way of static and dynamic fluorimetric kinetic determination and polypeptides analysis, the big light-harvesting complexes and PSⅡpellets were proved to be phycocyanin-chlorophyll-protein complexes. The connection of phycocyanin and chlorophyll-protein show non- structural tendency; The energy trapped by phycocyanin could transfer to PSⅡby Chla/c-pigment complexes or directly. Finally, the relationship between chlorophyll–protein complexes of Chroomonas placoidea and phycocyanin were established.