Localization of the prosthetic group ligands of cytochrome o terminal oxidase complex of Escherichia coli

The cytochrome o ubiquinol oxidase is one of two terminal oxidases present in the aerobic respiratory chain of E. coli. The cytochrome o complex has been purified and found to contain two protoheme IXs and one copper atom. Subsequently the gene encoding the cyo operon has been cloned. The research presented in this thesis focuses on the continued structural analysis of the cytochrome o oxidase complex including the following areas of interest: (i) the DNA sequence of the cyo operon, (ii) subunit analysis, (iii) localization of the prosthetic groups of this complex to specific subunits and (iv) determination of the histidines responsible for ligating the prosthetic groups of this complex.;The cyo DNA sequence presented here reveals that there are five open reading frames, cyo A, B, C, D, and E. Similarity searches performed on these putative subunits reveal that three of these ORFs are related to subunits II, I, and III of both bacterial and eukaryotic cytochrome c oxidases. The remaining two putative subunits have sequence similarity with subunits found in bacterial cytochrome c oxidases.;Immunological analyses of subclones of cyoA and cyoB demonstrate that they encode subunits II and I, respectively. Subsequent spectroscopic analysis of these subclones and the cyoBCDE subclone localize both the high and low-spin hemes associated with this complex to subunit I (cyoB) of the cytochrome o oxidase.;The alignment of subunit I from cytochrome o oxidase with the analogous subunit from over 23 different species of bacterial and eukaryotic aa...