Potentiometric and spectral studies with the two-subunit cytochrome aa3 from Paracoccus denitrificans. Comparison with the 13-subunit beef heart enzyme

Previous work from this laboratory has revealed a complex and interactive redox behavior for the active metal centers in beef heart cytochrome aa3. All of these centers are contained in two of the 13 subunits which make up the enzyme. The isolated cytochrome aa3 of Paracoccus denitrificans contains only two subunits. The purpose of the current investigation was to see if the complex redox behavior is dependent on the presence of the additional 11 peptides that are present in the mammalian enzyme. In this paper we report that the structurally simpler bacterial enzyme displays a redox behavior which is very similar to that seen with the mammalian enzyme. Therefore, the observed redox behavior does not depend on interactions involving the additional peptides.