Protein Dynamics

Protein Dynamics - Heme-Copper Oxidases

The heme-copper oxidases are a superfamily of enzymes whose task it is to reduce dioxygen to water and to convert the free energy from this reaction into a transmembrane protonmotive force. All of these enzymes have a heme-copper bimetallic center, which is the active site where the dioxygen chemistry is catalyzed.

We have employed both static low-temperature and time-resolved IR spectroscopy to probe the structure response to ligation reactions at the binuclear active site. The heme center binds carbon monooxide in place of dioxygen. This CO can be reversibly photolyzed to give a transiently unligated center. At low temperature, photolysis yields CO bound to the nearby copper atom. These three states, Fe-CO, Cu-CO, and unligated form the basis for our difference IR studies.

Low temperature spectra comparing mammalian and bacterial oxidase.

Identification of specific amino acid residues is facilitated using IR spectroscopy of mutant enzymes.

Time-resolved spectra of bacterial oxidase.

Time-resolved spectra of mammalian oxidase.