title: Subunit stoichiometry of the chloroplast photosystem I complex.
abstract: A native photosystem I (PS I) complex and a PS I core complex depleted of antenna subunits has been isolated from the uniformly 14C-labeled aquatic higher plant, Lemna. These complexes have been analyzed for their subunit stoichiometry by quantitative sodium dodecyl sulfate-polyacrylamide gel electrophoresis methods. The results for both preparations indicate that one copy of each high molecular mass subunit is present per PS I complex and that a single copy of most low molecular mass subunits is also present. These results suggest that iron-sulfur center X, an early PS I electron acceptor proposed to bind to the high molecular mass subunits, contains a single [4Fe-4S] cluster which is bound to a dimeric structure of high molecular mass subunits, each providing 2 cysteine residues to coordinate this cluster.
authors.affiliation: Division of Molecular Plant Biology, University of California, Berkeley 94720.
authors.forename: B D
authors.initials: BD
authors.lastname: Bruce
authors.forename: R
authors.initials: R
authors.lastname: Malkin
mesh_terms: D002250:Carbon Radioisotopes; D002734:Chlorophyll / Q000302:isolation & purification / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008970:Molecular Weight; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll