title: Bidirectional electron transfer in photosystem I: direct evidence from high-frequency time-resolved EPR spectroscopy.
abstract: Efficient charge separation occurring within membrane-bound reaction center proteins is the most important step of photosynthetic solar energy conversion. All reaction centers are classified into two types, I and II. X-ray crystal structures reveal that both types bind two symmetric membrane-spanning branches of potential electron-transfer cofactors. Determination of the functional roles of these pairs of branches is of fundamental importance. While it is established that in type II reaction centers only one branch functions in electron transfer, we present the first direct spectroscopic evidence that both cofactor branches are active in the type I reaction center, photosystem I.
authors.affiliation: Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA. oleg@anl.gov
authors.forename: Oleg G
authors.initials: OG
authors.lastname: Poluektov
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Paschenko
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Utschig
authors.forename: K V
authors.initials: KV
authors.lastname: Lakshmi
authors.forename: Marion C
authors.initials: MC
authors.lastname: Thurnauer
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004579:Electron Transport; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D013455:Sulfur; D007501:Iron