Three photosystem I(PSⅠ)particles associated with different amounts of light-harvesting complex I(LHCI)were isolated from a phycocyanin 645(PC645)-containing cryptophyte Chroomonas placoidea by Triton X-100 sucrose g...Three photosystem I(PSⅠ)particles associated with different amounts of light-harvesting complex I(LHCI)were isolated from a phycocyanin 645(PC645)-containing cryptophyte Chroomonas placoidea by Triton X-100 sucrose gradient centrifugation.Two active PSⅠ-LHCⅠparticles(Bands 4 and 5)were resolved from thylakoids stripped of cations only,which implied that LHC migration and the adjustment of energy distribution between photosystemⅡ(PSⅡ)and PSⅠfacilitated by cations could also occur in cryptophytes,like in higher plants.Peptide analysis revealed that 19.8-,10-,and 8.3-kDa peptides corresponding toβ,α1,andα2 subunits of PC645,respectively,were present in Bands 4 and 5.Analyses of fluorescence and circular dichroism spectra and Gauss analyses revealed efficient energy couplings between PC645 and chlorophyll within both of these PSⅠ-LHCⅠparticles.The excitation energy absorbed by PC645 could be directly transferred to chlorophyll a in the PSⅠcore or via the chlorophyll a/c-protein complex of LHCⅠ.Based on these observations,we designated the two PSⅠ-LHCⅠparticles as phycocyanin-PSⅠcomplexes,which have not been reported previously.Band 4-2 was a sub-complex of Band 4 and was almost depleted of LHCⅠ(the chlorophyll a/c-protein complex was designated as Band 4-1)and PC645.Therefore,Band 4-2 was recognized as the PSⅠcore complex.Negative staining and transmission electron microscopy images of Band 4 gave a direct view that the PC645 component attached with chlorophyll-protein complexes in a regular structure as hollow ring shape.Furthermore,while previous studies have indicated that PC645 associates with PSⅡ,our results reveal that,in this cryptophytic alga,PC645 exhibits structural—but not preferential—association with PSⅠ,which provided new information about the architecture and function of the energy transfer system comprising phycobiliproteins and chlorophyll-protein complexes in cryptophytes.展开更多
Photosystem I(PSI)is one of the two photosystems in photosynthesis,and performs a series of electron transfer reactions leading to the reduction of ferredoxin.In higher plants,PSI is surrounded by four light-harvestin...Photosystem I(PSI)is one of the two photosystems in photosynthesis,and performs a series of electron transfer reactions leading to the reduction of ferredoxin.In higher plants,PSI is surrounded by four light-harvesting complex I(LHCI)subunits,which harvest and transfer energy efficiently to the PSI core.The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6Åresolution,providing much information on the arrangement of proteins and cofactors in this complicated supercomplex.Here we have optimized crystallization conditions,and analyzed the crystal structure of PSI-LHCI at 2.4Åresolution.Our structure showed some shift of the LHCI,especially the Lhca4 subunit,away from the PSI core,suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core.We identified five new lipids in the structure,most of them are located in the gap region between the Lhca subunits and the PSI core.These lipid molecules may play important roles in binding of the Lhca subunits to the core,as well as in the assembly of the supercomplex.The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting,transfer and assembly of this supercomplex.展开更多
Purified PSI complexes from Spinacia Oleracea L. were exposed to the strong light (PFD=2300μmol m-2s-1) for various period. Along with the illumination the photo-damage process of pigments and proteins of PSI complex...Purified PSI complexes from Spinacia Oleracea L. were exposed to the strong light (PFD=2300μmol m-2s-1) for various period. Along with the illumination the photo-damage process of pigments and proteins of PSI complexes was investigated using absorption, fluorescence, circular dichroism (CD) spectroscopy and SDS-PAGE. It was found from the optical absorption spectra that the maximal ab-sorbance of PSI complexes decreased and maximal peaks blue-shifted during the illumination, and the forth derivative spectra demonstrated that the absorbance decreasing at red region mainly resulted from the aborbance decreasing of the long wavelength Chla, implying that the long-wavelength Chla was readily to be bleached. The CD signals contributed by LHCI decreased more rapidly than other CD signals con-tributed by Chla and Carotenoid, indicating that the LHCI was more sensitive to light than core complexes. It was observed by SDS-PAGE that some small polypeptides of PSI complexes were damaged earlier than reaction展开更多
基金Supported by the Natural Science Foundation of Shandong Province(No.ZR2018LD009)。
文摘Three photosystem I(PSⅠ)particles associated with different amounts of light-harvesting complex I(LHCI)were isolated from a phycocyanin 645(PC645)-containing cryptophyte Chroomonas placoidea by Triton X-100 sucrose gradient centrifugation.Two active PSⅠ-LHCⅠparticles(Bands 4 and 5)were resolved from thylakoids stripped of cations only,which implied that LHC migration and the adjustment of energy distribution between photosystemⅡ(PSⅡ)and PSⅠfacilitated by cations could also occur in cryptophytes,like in higher plants.Peptide analysis revealed that 19.8-,10-,and 8.3-kDa peptides corresponding toβ,α1,andα2 subunits of PC645,respectively,were present in Bands 4 and 5.Analyses of fluorescence and circular dichroism spectra and Gauss analyses revealed efficient energy couplings between PC645 and chlorophyll within both of these PSⅠ-LHCⅠparticles.The excitation energy absorbed by PC645 could be directly transferred to chlorophyll a in the PSⅠcore or via the chlorophyll a/c-protein complex of LHCⅠ.Based on these observations,we designated the two PSⅠ-LHCⅠparticles as phycocyanin-PSⅠcomplexes,which have not been reported previously.Band 4-2 was a sub-complex of Band 4 and was almost depleted of LHCⅠ(the chlorophyll a/c-protein complex was designated as Band 4-1)and PC645.Therefore,Band 4-2 was recognized as the PSⅠcore complex.Negative staining and transmission electron microscopy images of Band 4 gave a direct view that the PC645 component attached with chlorophyll-protein complexes in a regular structure as hollow ring shape.Furthermore,while previous studies have indicated that PC645 associates with PSⅡ,our results reveal that,in this cryptophytic alga,PC645 exhibits structural—but not preferential—association with PSⅠ,which provided new information about the architecture and function of the energy transfer system comprising phycobiliproteins and chlorophyll-protein complexes in cryptophytes.
基金supported by the National Key Research and Development Program of China(2017YFA0503700)the Chinese Academy of Sciences Key Research Program of Frontier Sciences(QYZDY-SSW-SMC003)+5 种基金a Strategic Priority Research Program of CAS(XDB17000000)a National Basic Research Program of China(2015CB150100)the National Natural Science Foundation of China(31622007,31670237,32070267)the Youth Innovation Promotion Association of CAS(2020081)Taishan Scholars Project,Jinan Science and Technology Project(2020GXRC058)the Natural Science Foundation of Shandong Province China(ZR2019ZD48).
文摘Photosystem I(PSI)is one of the two photosystems in photosynthesis,and performs a series of electron transfer reactions leading to the reduction of ferredoxin.In higher plants,PSI is surrounded by four light-harvesting complex I(LHCI)subunits,which harvest and transfer energy efficiently to the PSI core.The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6Åresolution,providing much information on the arrangement of proteins and cofactors in this complicated supercomplex.Here we have optimized crystallization conditions,and analyzed the crystal structure of PSI-LHCI at 2.4Åresolution.Our structure showed some shift of the LHCI,especially the Lhca4 subunit,away from the PSI core,suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core.We identified five new lipids in the structure,most of them are located in the gap region between the Lhca subunits and the PSI core.These lipid molecules may play important roles in binding of the Lhca subunits to the core,as well as in the assembly of the supercomplex.The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting,transfer and assembly of this supercomplex.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 39890390) the State Key Basic Research and Development Program (Grant No. G1998010100) and the Innovative Foundation of Laboratory of Photosynthesis Basic Research
文摘Purified PSI complexes from Spinacia Oleracea L. were exposed to the strong light (PFD=2300μmol m-2s-1) for various period. Along with the illumination the photo-damage process of pigments and proteins of PSI complexes was investigated using absorption, fluorescence, circular dichroism (CD) spectroscopy and SDS-PAGE. It was found from the optical absorption spectra that the maximal ab-sorbance of PSI complexes decreased and maximal peaks blue-shifted during the illumination, and the forth derivative spectra demonstrated that the absorbance decreasing at red region mainly resulted from the aborbance decreasing of the long wavelength Chla, implying that the long-wavelength Chla was readily to be bleached. The CD signals contributed by LHCI decreased more rapidly than other CD signals con-tributed by Chla and Carotenoid, indicating that the LHCI was more sensitive to light than core complexes. It was observed by SDS-PAGE that some small polypeptides of PSI complexes were damaged earlier than reaction
