title: Iron-sulfur clusters in type I reaction centers.
abstract: Type I reaction centers (RCs) are multisubunit chlorophyll-protein complexes that function in photosynthetic organisms to convert photons to Gibbs free energy. The unique feature of Type I RCs is the presence of iron-sulfur clusters as electron transfer cofactors. Photosystem I (PS I) of oxygenic phototrophs is the best-studied Type I RC. It is comprised of an interpolypeptide [4Fe-4S] cluster, F(X), that bridges the PsaA and PsaB subunits, and two terminal [4Fe-4S] clusters, F(A) and F(B), that are bound to the PsaC subunit. In this review, we provide an update on the structure and function of the bound iron-sulfur clusters in Type I RCs. The first new development in this area is the identification of F(A) as the cluster proximal to F(X) and the resolution of the electron transfer sequence as F(X)-->F(A)-->F(B)-->soluble ferredoxin. The second new development is the determination of the three-dimensional NMR solution structure of unbound PsaC and localization of the equal- and mixed-valence pairs in F(A)(-) and F(B)(-). We provide a survey of the EPR properties and spectra of the iron-sulfur clusters in Type I RCs of cyanobacteria, green sulfur bacteria, and heliobacteria, and we summarize new information about the kinetics of back-reactions involving the iron-sulfur clusters.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 310 South Frear Building, University Park, PA 16802, USA.
authors.forename: I R
authors.initials: IR
authors.lastname: Vassiliev
authors.forename: M L
authors.initials: ML
authors.lastname: Antonkine
authors.forename: J H
authors.initials: JH
authors.lastname: Golbeck
mesh_terms: D019414:Chlorobi / Q000737:chemistry*; D000458:Cyanobacteria / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D045342:Light-Harvesting Protein Complexes; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins; D008958:Models, Molecular; D015394:Molecular Structure; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045331:Photosystem I Protein Complex; D011506:Proteins / Q000737:chemistry
chemical_list: D007506:Iron-Sulfur Proteins; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D011506:Proteins; C089909:photosystem I, psaB subunit