Structure and function of NO-reducing heme-copper oxidases

Project leader

Funding source

Swedish Research Council - Vetenskapsrådet (VR)

Project Details

Start date: 01/01/2009
End date: 31/12/2011
Funding: 2100000 SEK


Bacterial NO-reductases (NOR) are membrane proteins that reduce the toxic gas nitric oxide (NO) to dinitrous oxide (N2O) (2NO+2e-+2H+-->N2O+H2O). This reaction is a step in denitrification, an anaerobic process where nitrate (NO3-) is reduced stepwise to dinitrogen gas. NOR is also found in pathogenic bacteria, where its role is to detoxify the NO produced by the host´s immune defense. NORs are divergent members of the super-family of oxygen-reducing heme-copper oxidases (HCuOs), to which the mitochondrial cytochrome c oxidase (CcO) also belongs. Despite belonging to the same family, the function of the NORs is very different from other HCuOs, for example NORs do not conserve the free energy available from its reaction by creating a proton electrochemical gradient over the membrane. The closest relatives to NOR among the HCuOs are the cbb3 oxidases, which have a high oxygen affinity and are found exclusively in bacteria, often pathogens. The cbb3 oxidases also have NO-reduction activity in contrast to the CcOs, and NORs can reduce O2. The project aims at elucidating the structure and function of the bacterial NORs and cbb3 oxidases, with special focus on their cross-reactivities with O2 and NO. We expect to gain insight also into the evolution of the heme-copper oxidases. Our studies involve using time-resolved optical spectroscopy, molecular biology, modeling, and protein crystallography. We study the wildtype enzymes as well as engineered mutant forms.

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