Structure and Function of bacterial NO-reductases and cbb3-type oxidases

Project leader

Funding source

Swedish Research Council - Vetenskapsrådet (VR)

Project Details

Start date: 01/01/2007
End date: 31/12/2009
Funding: 1500000 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, a process in which nitrate (NO3-) is used as the terminal electron acceptor and reduced stepwise to dinitrogen gas. NORs are also found in pathogenic bacteria, where its role is to detoxify the NO produced by the host’s immune defense. NORs have been found to be 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 believed to very different from the HCuOs. The closest relatives to NOR among the HCuOs are the cbb3 oxidases, which have a high oxygen affinity and are found exclusively in bacteria, e.g. pathogens and denitrifiers. The cbb3 oxidases have recently been shown to have NO-reduction activity in contrast to the CcOs. The project aims at elucidating the structure and function of the bacterial NORs and cbb3 oxidases, with special focus on their ‘cross-reactivity’ with O2 and NO. These studies are expected to give insight also into the evolution of the heme-copper oxidases. The structure and function of the NORs and cbb3 oxidases are investigated by time-resolved optical spectroscopy, molecular biology, molecular modeling, and protein crystallography. The wild-type enzymes as well engineered mutant forms are studied.

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