【摘 要】
：
An active photosystem(PS)Ⅱ particle and two light-harvesting complexes,as well as their sub-complexes that have not been reported previously,were isolated from a cryptophyte Chroomonas placoidea by Triton X-100 sucrose density gradient centrifugation.The
【机 构】
：
Institute of Life Science,Yantai University,Yantai 264005,China
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An active photosystem(PS)Ⅱ particle and two light-harvesting complexes,as well as their sub-complexes that have not been reported previously,were isolated from a cryptophyte Chroomonas placoidea by Triton X-100 sucrose density gradient centrifugation.The fluorescence spectra revealed that there were efficient energy couplings between phycocyanin(PC645)and chlorophyll(Chl)within both zones Ⅲ andⅣ of the gradient,which were designated respectively as light-harvesting complex and PSⅡ particles whose size was 15-20 nm according to negative staining in electron microscopy.When the two complexes were further resolved into sub-complexes,the energy coupling was retained in the core PSⅡ complex(named as zone Ⅳ-2 of the sucrose gradient),which contained almost no outer antenna pigment Chl c.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)showed that the PC645 components appeared in Chl-containing protein complexes were mainly the β subunit with molecular weight of 20 kDa.These results demonstrate that PC645 in this cryptophyte was structurally but preferentially combined with the light-harvesting complex and PSⅡ core.The excitation energy absorbed by PC645 could be directly transferred to Chl a(especially the long wavelength of Chl a)in the PSⅡ reaction center or via the Chl a/c-protein complex.The β subunit corresponded to the terminal fluorescence emission and might play an important role in transmitting energy from PC645 to the Chl-protein complex.The results will help in elucidating the architecture and function of the energy transfer system comprising phycobiliproteins and Chl-protein complexes in cryptophytes.
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