Abstract
Photosystem I（PSI）absorbs and utilizes light energy to generate reducing power for the reduction of NADP＋ to NADPH with a quantum efficiency close to 100%. Plant PSI forms a supercomplex with light-harvesting complex I（LHCI）with a total molecular weight of over 600 kDa．X-ray structure analysis of the PSI-LHCI membrane-protein supercomplex has revealed detailed arrangement of the light-harvesting pigments and other cofactors especially within LHCI．Here the excited energy transfer（EET）pathways from LHCI to the PSI core and photoprotection mechanisms are discussed based on the structure obtained.
