Multiple scattering x-ray absorption studies of Zn2+ binding sites in bacterial photosynthetic reaction centers.

ABSTRACT: Binding of transition metal ions to the reaction center (RC) protein of the photosynthetic bacterium Rhodobacter sphaeroides has been previously shown to slow light-induced electron and proton transfer to the secondary quinone acceptor molecule, Q(B). On the basis of x-ray diffraction at 2.5 angstroms resolution a site, formed by AspH124, HisH126, and HisH128, has been identified at the protein surface which binds Cd(2+) or Zn(2+). Using Zn K-edge x-ray absorption fine structure spectroscopy we report here on the local structure of Zn(2+) ions bound to purified RC complexes embedded into polyvinyl alcohol films. X-ray absorption fine structure data were analyzed by combining ab initio simulations and multiparameter fitting; structural contributions up to the fourth coordination shell and m

SUBMITTER: Giachini L 

PROVIDER: S-EPMC1305256 | biostudies-literature | 2005 Mar

REPOSITORIES: biostudies-literature