NO-reducing heme-copper oxidases

Project leader

Funding source

Swedish Research Council - Vetenskapsrådet (VR)

Project Details

Start date: 01/01/2012
End date: 31/12/2014
Funding: 2000000 SEK


Bacterial denitrification is a crucial part of the nitrogen cycle in nature. The bacterial nitric oxide reductases (NOR) are part of the denitrification pathway, reducing nitric oxide (NO) to nitrous oxide (N2O). Sequence alignments have shown that NORs belong to the super-family of the oxygen-reducing heme-copper oxidases (HCOs), of which the mitochondrial cytochrome c oxidase is a member. Among the HCOs, the closest relative to the NORs are the more ‘primitive’ cbb3-type oxidases, which interestingly are the traditional HCOs that show the highest NO-reduction activity, indicating a relationship between catalytic specificity and evolutionary distance. Whereas there is a wealth of information on the mechanism of both structure and mechanism of action of the ‘traditional’ heme copper oxidases, much less is known about the NORs and cbb3-type oxidases. The project aims at elucidating the structure and function of the membrane-bound bacterial NO-reductases as well as the cbb3-type oxidases. We are studying detergent-solubilised purified enzymes as well as enzymes reconstituted into lipid vesicles. The role of individual amino acids is investigated using site-directed mutagenesis, and results are analysed in terms of 3D computer models of the catalytic subunit. Our current focus is on functional studies of electron and proton transfer reactions as well as the mechanism of O2 and NO-reduction using time-resolved (from microseconds) optical spectroscopy and electrometry in combination with stopped-flow and flash photolysis methods.

Last updated on 2017-31-03 at 12:57