title: The three-dimensional structure of the FMO protein from Pelodictyon phaeum and the implications for energy transfer.
abstract: The Fenna-Matthews-Olson (FMO) antenna protein from the green bacterium Pelodictyon phaeum mediates the transfer of energy from the peripheral chlorosome antenna complex to the membrane-bound reaction center. The three-dimensional structure of this protein has been solved using protein crystallography to a resolution limit of 2.0 Å, with R(work) and R(free) values of 16.6 and 19.9%, respectively. The structure is a trimer of three identical subunits related by a threefold symmetry axis. Each subunit has two beta sheets that surround 8 bacteriochlorophylls. The bacteriochlorophylls are all five-coordinated, with the axial ligand being a histidine, serine, backbone carbonyl, or bound water molecule. The arrangement of the bacteriochlorophylls is generally well conserved in comparison to other FMO structures, but differences are apparent in the interactions with the surrounding protein. In this structure the position and orientation of the eighth bacteriochlorophyll is well defined and shows differences in its location and the coordination of the central Mg compared to previous models. The implications of this structure on the ability of the FMO protein to perform energy transfer are discussed in terms of the experimental optical measurements.
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA.
authors.forename: Chadwick R
authors.initials: CR
authors.lastname: Larson
authors.forename: Chenda O
authors.initials: CO
authors.lastname: Seng
authors.forename: Lisa
authors.initials: L
authors.lastname: Lauman
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Matthies
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Wen
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
authors.forename: James P
authors.initials: JP
authors.lastname: Allen
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D019414:Chlorobi / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004735:Energy Transfer; D021621:Imaging, Three-Dimensional; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes