Characterization of the Polypeptide Components of the Cytochrome BC 1 Complex of Rhodobacter sphaeroides

Abstract

The ubiquinol-cytochrome c 2 oxidoreductase (cytochrome bc 1 complex) of Rhodobacter sphaeroides is an integral component of the intracytoplasmic membrane (ICM) and functions in light-driven cyclic electron flow and the conservation of radiant energy as an electrochemical proton gradient. Previous studies on the assembly of electron transfer constituents in R. sphaeroides have demonstrated that complete cycles of electron flow do not occur merely upon insertion of newly synthesized reaction centers at sites of initiation of ICM growth, but instead, subsequent synthesis and assembly of redox centers of the bc 1 complex are required [1]. To further characterize the assembly process and for detailed structural investigations, the complex was purified and antibodies were raised against the isolated polypeptide constituents. In this report, results on the localization and levels of the bc 1 complex in various membrane fractions are presented; a detailed description of the structural work will appear elsewhere [2].