tailieunhanh - Báo cáo Y học: An alternative model for photosystem II/light harvesting complex II in grana membranes based on cryo-electron microscopy studies

The photosynthetic protein complexes in plants are located in the chloroplast thylakoid membranes. These membranes have an ultrastructure that consists of tightly stackedÔgranaÕ regions interconnectedbyunstackedmembrane structure of isolated granamembranes has been studiedhere by cryo-electron microscopy. The data reveals an unusual arrangement of the photosynthetic protein complexes, staggered over two tightly stacked planes. | Eur. J. Biochem. 269 326-336 2002 FEBS 2002 An alternative model for photosystem II light harvesting complex II in grana membranes based on cryo-electron microscopy studies Robert C. Ford1 Svetla S. Stoylova2 and Andreas Holzenburg3 1 Department of Biomolecular Sciences UMIST Manchester UK 2The Burnham Institute La Joua CA USA 3Department of Biology and Department of Biochemistry and Biophysics Microscopy and Imaging Center Texas A M University College Station TX USA The photosynthetic protein complexes in plants are located in the chloroplast thylakoid membranes. These membranes have an ultrastructure that consists of tightly stacked grana regions interconnected by unstacked membrane regions. The structure of isolated grana membranes has been studied here by cryo-electron microscopy. The data reveals an unusual arrangement of the photosynthetic protein complexes staggered over two tightly stacked planes. Chaotrope treatment of the paired grana membranes has allowed the separation and isolation of two biochemically distinct membrane fractions. These data have led us to an alternative model of the ultrastructure of the grana where segregation exists within the grana itself. This arrangement would change the existing view of plant photosynthesis and suggests potential links between cyanobacterial and plant photosystem II light harvesting systems. Keywords photosynthesis structure photosystem II lightharvesting electron crystallography. Photosynthesis one of the most important biochemical processes occurs in the thylakoid membranes of plants that are located inside specialized cell compartments chloroplasts . The thylakoid membrane system is highly organized with characteristic stacks of membranes that are termed grana which are interconnected by unstacked regions of membrane see Fig. 1A . In the classical view of plant photosynthesis one part of the photosynthetic electron transfer chain photosystem II is segregated into the grana whilst other components of the .