title: Crystal structure of plant photosystem I.
abstract: Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4 A resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.
authors.affiliation: Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Adam
authors.initials: A
authors.lastname: Ben-Shem
authors.forename: Felix
authors.initials: F
authors.lastname: Frolow
authors.forename: Nathan
authors.initials: N
authors.lastname: Nelson
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins; D002734:Chlorophyll / Q000737:chemistry; D061146:Chlorophyll Binding Proteins; D018360:Crystallography, X-Ray; D019281:Dimerization; D004579:Electron Transport; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000737:chemistry*; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D010970:Plastocyanin / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry; D010837:Vitamin K 1 / Q000737:chemistry
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; C490278:LHCA1 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D021122:Protein Subunits; C089909:photosystem I, psaB subunit; D002734:Chlorophyll; D010837:Vitamin K 1; D010970:Plastocyanin