Engineered Proteins

Current efforts by chemists to design sustainable catalysts often focus on replacing heavy metals with Earth-abundant metals that are less harmful to the environment. However, the supporting ligands are another potentially expensive, toxic component of a catalyst. We envision catalysts that are instead composed of non-toxic iron ions, supported by protein scaffolds that are completely biodegradable. This strategy is inspired by enzymes, many of which contain iron; however, natural enzymes have evolved to meet the challenges of survival rather than the broader range of synthetic challenges faced by chemists in the 21st century. Thus, we modify the metalloproteins to encourage new reactivity.

Our first foray into this area used the small protein apo-azurin, which in nature holds a low-coordinate copper center. By substituting iron in the active site and changing the surroundings of the metal site, we were able to bind cyanide and azide. It was also reduced to the unusual iron(I) oxidation state. In future work, we aim to create catalysts with other iron-protein assemblies.

Relevant Publications

Nicholas A. Arnet, Thomas R. Dugan, Fabian S. Menges, Brandon Q. Mercado, William W. Brennessel, Eckhard Bill, Mark A. Johnson, Patrick L. Holland
Synthesis, Characterization, and Nitrogenase-Relevant Reactions of an Iron Sulfide Complex with a Bridging Hydride
J. Am. Chem. Soc.  2015137, 13220-13223.  highlight in Nature Chemical Biology
Roman M. Davydov, Matthew P. McLaughlin, Eckhard Bill, Brian M. Hoffman, Patrick L. Holland
Generation of High-Spin Iron(I) in a Protein Environment Using Cryoreduction
Inorg. Chem.  201352, 7323-7325.  
Matthew P. McLaughlin, Marius Retegan, Eckhard Bill, Thomas M. Payne, Hannah S. Shafaat, Salvador Peña, Jawahar Sudhamsu, Amy E. Ensign, Brian R. Crane, Frank Neese, Patrick L. Holland
Azurin as a protein scaffold for a low-coordinate non-heme iron site with a small-molecule binding pocket
J. Am. Chem. Soc.   2012134, 19746-19757.  
Matthew P. McLaughlin, Thomas H. Darrah, Patrick L. Holland
Palladium(II) and platinum(II) bind strongly to an engineered blue copper protein
Inorg. Chem.   201150, 11294-11296.