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Project: Nitric oxide reductase |
Rob van Spanning Department of Molecular Cell Physiology vrije Universiteit amsterdam |
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2D image of a dimer of NOR (Saraste Heidelberg)
| Many species of bacteria contain a nitric oxide reductase (NOR), which reduces nitric oxide (NO) to nitrous oxide. NOR belongs to the superfamily of terminal oxidases, which also includes the aa3-type terminal oxidase, responsible for the reduction of molecular oxygen to water and hence for much of biological energy metabolism in many organisms. By implication, their common ancestor of more than 2 billion years ago may have been a protein resembling NOR. Much of the structure and function of the terminal oxidases is known, but the catalytic mechanism of oxygen reduction and its coupling to proton pumping are not yet fully understood. To some extent this is because there are no comparative studies of enzymes that are related to the oxidases, but differ in key aspects of structure and function. NOR may be such an enzyme: against the backdrop of the overall similarities in structure and function, NOR differs in two functional and two structural aspects from the oxidases. The functional differences are that NOR reduces NO at a higher rate than oxygen (whereas the oxidases reduce NO at a lower rate than oxygen) and that it appears to pump fewer if any protons. The structural differences are the presence of iron rather than copper in the binuclear metal center that is responsible for the reduction of oxygen or NO, and the precise amino acid residues that reside in the alpha helices around the catalytic center. It was the objective of a EC Biotech proposal (SENORA) to determine whether these structural differences are responsible for the functional differences and hence generate a deeper insight into the structural evolution and catalytic mechanism of the superfamily of terminal oxidases. | ||
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© November 4 2001 Rob van Spanning Home Page Rob van Spanning webmaster: Daoud Sie |
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