title: Photosystem I of Chlamydomonas reinhardtii contains nine light-harvesting complexes (Lhca) located on one side of the core.
abstract: In this work we have purified the Photosystem I (PSI) complex of Chlamydomonas reinhardtii to homogeneity. Biochemical, proteomic, spectroscopic, and structural analyses reveal the main properties of this PSI-LHCI supercomplex. The data show that the largest purified complex is composed of one core complex and nine Lhca antennas and that it contains all Lhca gene products. A projection map at 15 Å resolution obtained by electron microscopy reveals that the Lhcas are organized on one side of the core in a double half-ring arrangement, in contrast with previous suggestions. A series of stable disassembled PSI-LHCI intermediates was purified. The analysis of these complexes suggests the sequence of the assembly/disassembly process. It is shown that PSI-LHCI of C. reinhardtii is larger but far less stable than the complex from higher plants. Lhca2 and Lhca9 (the red-most antenna complexes), although present in the largest complex in 1:1 ratio with the core, are only loosely associated with it. This can explain the large variation in antenna composition of PSI-LHCI from C. reinhardtii found in the literature. The analysis of several subcomplexes with reduced antenna size allows determination of the position of Lhca2 and Lhca9 and leads to a proposal for a model of the organization of the Lhcas within the PSI-LHCI supercomplex.
authors: Department of Biophysical Chemistry, Groningen Biological Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors: Bartlomiej
authors: B
authors: Drop
authors: Mariam
authors: M
authors: Webber-Birungi
authors: Fabrizia
authors: F
authors: Fusetti
authors: Roman
authors: R
authors: Kouřil
authors: Kevin E
authors: KE
authors: Redding
authors: Egbert J
authors: EJ
authors: Boekema
authors: Roberta
authors: R
authors: Croce
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex