Current Projects in the Vaden Research Group

Crystal structure of three proteins (Cu(I/II) in green) for bioremediation development. A: Pseudoazurin-NiR complex (PDB id: 5B1J); B: Azurin (PDB id: 4MFH); C: NiR (PDB id: 1MZY); D: Laccase (PDB id: 1GYC).

Denitrification is the process of reducing soil/water nitrates into atmospheric nitrogen. Excess nitrates from fertilizers and industry can cause atmospheric problems due to generation of NO_x pollutants and the greenhouse-gas N₂O, which are denitrification intermediates. A key step in bacterial denitrification is the NO₂^- to NO reduction at the nitrite reductase (NiR)/azurin redox protein system. Azurin, bound to NiR, transfers the electrons via the Cu (I/II) metallocenter. Utilizing this protein system for engineered denitrification has potential for industrial-scale environmental remediation, especially in the removal of nitrates from contaminated water. If it can be selectively stabilized and enhanced in non-physiological environments, NiR/azurin may be exploited for environmentally-friendly industrial and environmental chemistry. Together, the complex can be isolated and utilized for environmental remediation. Separately, azurin can be targeted for electrochemistry and the NiR enzyme can catalyze nitrogen-based chemistry. By altering the protein structures and copper metallocenters the copper reduction voltages can be tuned to modulate protein activities. Hence, it should be possible to selectively enhance NiR and azurin by using solution additives to stabilize or destabilize their structures.