CHARACTERIZATION OF FLAVOCYTOCHROME-C(552) FROM THE THERMOPHILIC PHOTOSYNTHETIC BACTERIUM CHROMATIUM TEPIDUM

A M(r) 68 kDa flavocytochrome c(552) has been isolated from the thermo philic photosynthetic purple sulfur bacterium Chromatium tepidum and s hown to consist of a M(r) 25 kDa subunit that contains two covalently bound heme c and a M(r) 43 kDa subunit that probably contains a single FAD. The prosthetic group content, absorbance spectra, and subunit co mposition of the C. tepidum flavocytochrome are quite similar to those previously reported for the flavocytochrome c(552) isolated from a me sophilic Chromatium species, Chromatium vinosum. The oxidation-reducti on properties of the hemes present in the C. tepidum flavocytochrome h ave been characterized by titrations, the effect of temperature on the catalytic activity of the protein has been investigated, and the heme environment has been characterized using resonance Raman spectroscopy . (C) 1994 Academic Press, Inc.