Studies on the Iron-Binding Site of Bacterial Reaction Centers

Abstract

Most reaction center preparations from photosynthetic bacteria are usually isolated as a complex of three polypeptides (H, H and L) and contain, besides other cofactors, nonheme iron in stoichiometric quantities. The exact structural arrangement of the various components of the reaction center is not yet established. However subunit H could be separated from the M-L complex without loss of photochemical activity (Okamura et al., 1974). Marinetti et al. (1979) showed that the primary quinone binding site is located on or close to the M subunit, whereas Gimenez-Gallego et al. (1982) found that even subunit L alone retains the characteristic absorption spectrum and the photochemical activity. We found no report so far on the binding site of the nonheme iron and therefore decided to study the iron binding site of the reaction center of Rho do spirillum rubrum using radioactive labeling and electrophoretic techniques.