Assembly of nitrous oxide reductase, a key enzyme in climate change

LEBRUN_U20DTP1

Nitrous oxide (N2O) is a greenhouse gas with a ~300 fold greater global warming potential than CO2 and an ability to deplete stratospheric ozone. Much of the N2O generated arises from activity of soil bacteria that are able to grow anaerobically through denitrification, a process central to the biogeochemical cycling of nitrogen, in which nitrate is reduced stepwise to dinitrogen (N2) via nitrite, nitric oxide (NO), and N2O.

The last step of the pathway, reduction of N2O to the environmentally harmless N2, is catalysed by the enzyme nitrous oxide reductase (N2OR); failure of this step to occur is the major cause of N2O release into the atmosphere. Atmospheric levels of N2O are increasing, in large part due to the increased use in agriculture of nitrogenous fertilisers.

N2OR is a soluble homodimeric enzyme, with each subunit composed of two domains. One binds CuA,a thiol-bridged dinuclear copper centre, while the other binds CuZ, a unique tetranuclear Cu cluster that also contains sulfide. Assembly of the Cu cofactors of N2OR occurs in the periplasm and is dependent on a number of assembly proteins whose functions are, in most cases, not well defined.

This project aims to provide new molecular detail of the trafficking of copper and sulfide within the bacterial cell for assembly of Cu centres of N2OR, leading to new insights into the biogenesis of N2OR that will feed into long-term efforts towards maximising N2OR activity in soils, thereby reducing N2O emissions.

This multi-disciplinary project will be based in the Le Brun and Gates labs at UEA and the Balk lab at John Innes Centre and will involve microbiology, protein purification, biochemistry and bioanalytical techniques, offering excellent training potential for the appointed student within a supportive and stimulating environment.