Tweaked Protein Conducts Electrons Faster

Making an electron-transfer protein more flexible can help it conduct electrons more readily. This finding could help researchers improve the efficiency of energy-conversion processes such as photosynthesis and respiration. A theory developed by Rudolph A. Marcus of Caltech, for which he won the 1992 Nobel Prize in Chemistry, states that lowering a protein’s reorganization energy—the energy required to rearrange a protein’s internal structure during electron transfers—makes such transfers speedier. The rational design of protein electron-transfer centers to lower reorganization energies has rarely been demonstrated. Now, Yi Lu of the University of Illinois, Urbana-Champaign, and coworkers show that engineering the electron-transfer protein azurin by modifying hydrophobicity or hydrogen-bonding of residues around the protein’s copper center makes the residues interact with one another more flexibly, lowering the protein’s reorganization energy and improving its electron-transfer efficiency (Proc. Natl. Acad. Sci. USA 2013, DOI: 10.1073/pnas.1215081110). The findings could lead to “a deeper understanding of electron transfer in other systems and the de novo design of electron-transfer proteins for applications such as advanced energy conversion,” Lu says.