LOW-TEMPERATURE SPECTROSCOPY OF ISOLATED FMO-PROTEIN AND A MEMBRANE-FREE REACTION-CENTER COMPLEX FROM THE GREEN SULFUR BACTERIUM CHLOROBIUM-TEPIDUM

We have isolated the water-soluble BChl a-protein (FMO-protein) from t he green sulfur bacterium Chlorobium tepidum by a new procedure involv ing a salt-wash of isolated membranes at alkaline pH. The absorption s pectrum of the isolated FMO-protein at 77 K was compared with that of a reaction-center complex containing the FMO-protein (FMO-RC complex) isolated from C. tepidum following the procedure of Feiler U, Nitsche W and Michel H (1992) Biochemistry 31: 2608-2614. Oxidation or illumin ation of the FMO-RC complex caused bleaching of a component with a max imum at 836 nm which was not present in the purified FMO-protein.