All aerobic cells transfer electrons from foodstuffs to oxygen to obtain energy in the form of ATP for their basic life processes. This conservation of energy during these reactions of electron transport is a vital cellular process, but its mechanism is poorly understood. Vitreoscilla is a bacterium that contains only heme B type respiratory pigments in its unique and relatively simple electron transport chain and can thus serve as a model for more complex chains. The long term goal of this proposed research is to elucidate the mechanism of electron transport from substrates to oxygen in Vitreoscilla, to learn the role of each electron carrier in this chain, and to obtain a better understanding of the process of energy conservation in this simple organism.
The specific aims of the project include learning the sequence of electron transfer in Vitreoscilla and purifying the proteins in this sequence. Antibodies against these purified proteins will be used as probes for studying the function of each individual electron transfer component. In addition, these antibodies will allow a comparison of the membrane-bound cytochrome o(m) with the soluble cytochrome o(s) so that their respective roles in electron transport can be ascertained. Cyanide and carbon monoxide resistant mutants will also be used to examine the role of these cytochromes in electron transport. The reconstitution of apocytochrome o(s) with porphyrins and metalloporphyrins will provide an understanding of the interaction of side groups on the heme and amino acid residues of the apoprotein and the reaction of the cytochrome with oxygen and ligands. Nuclear magnetic resonance spectroscopy will be employed for the latter studies of the heme environment. Other methods that will be employed are from the disciplines of protein chemistry, enzymology, and immunology. These studies will result in a better understanding of the reactions of electron transport in Vitreoscilla, information which may be extrapolated to more complex systems.
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