bullet1 Research Projects

Copper Proteins: Electron transfer and denitrification

Living organisms are able to move electrons over considerable distances with high specificity and efficiency. In fact it is the flow of electrons through the metabolic network that sustains all life. Thus, it is not surprising that much effort has been devoted to understanding the mechanisms of biological electron transfer at a molecular level. Bacteria use a wide variety of different electron transport pathways and many of the proteins involved in these reactions contain copper.

In collaboration with the Biological Chemistry Department at the John Innes Centre, we have carried out a systematic structural studies of several proteins associated with the denitrification. These include the copper proteins azurin and nitrite reductase, present in the denitrification pathway of the bacterium alcaligenes xylosoxidans.

We have also undertaken extensive molecular biological and structural studies of the small blue copper protein rusticyanin. this protein is thought to be a principal component in the iron respiratory electron transport chain of Thiobacillus ferrooxidans. Rusticyanin possesses the highest redox potential of the type 1 Cu proteins (680mV compared to more typical values of ~300mV) and has extreme acid stablility, being active at pH 2.

Nitrogenase: Proteins involved in nitrogen fixation

Fixing atmospheric nitrogen into ammonia and nitrates, forms usable to plants, is essential for plant growth. Nitrogen is fixed in three ways; spontaneously by lightning, combustion and photochemical reactions, industrially using the Haber process to make fertilisers, and biologically by nitrogen fixing bacteria. Nitrogenase, the enzyme responsible for biological nitrogen fixation, catalyses the ATP dependent reduction of dinitrogen to ammonia, accounts for 60% of the nitrogen fixed. A two components system catalyse the first step of nitrogen fixation. The first binds the nitrogen in an iron molybdenum or iron vanadium cluster. The second transfers electron to the first, which reduce the nitrogen.

We have studied that structures of the iron sulphur and molybdenum/vanadium iron components of the nitrogen fixing systems of Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum.

Superoxide Dismutase: Scavenging free radicals

Copper zinc superoxide dismutase protects cells from oxygen toxicity by catalysing the dismutation of superoxide into molecular oxygen and hydrogen peroxide. The importance of this enzyme lies in its ability to scavenge these toxic superoxide free radicals. although these free radicals are a normal byproduct of metabolism, they are responsible for the breakdown of biological macromolecules and thus contribute to such conditions as aging and cancer. In humans, superoxide dismutase has been implicated in the neurodegenerative disease Familial Amyotrophic Lateral Sclerosis, and so has been the subject of intense scrutiny.

The research programme of the MBG is supported by BBSRC, EPSRC and CCLRC.