Center for Biological Electron Transfer and Catalysis

Flavins play pivotal roles in energy conservation in electron transfer. This is because they are able to accept electrons in pairs from moderately reducing sources but deliver them one-at-a-time to other recipients. Most importantly for this project, the flavin can be converted to a form that is a very potent 1-electron reductant by the reaction of a strong 1-electron oxidant with the 2-electron reduced flavin. The Miller group will be studying exemplars of the proteins that mediate this chemistry: members of the electron transfer flavoprotein family (ETFs), to learn how specific interactions between the protein and the flavin imbue the flavin with the correct reduction midpoint potentials (E°) to be able to undertake this chemistry. Moreover we will also determine how the E°s are changed upon formation of protein complexes between the ETF and the proteins that donate electrons to it or acquire electrons from it. Thus we will use various spectroscopic methods in conjunction with spectroelectrochemistry to measure E°s, and stopped-flow spectrophotometry to detect transient intermediates of electron transfer and characterize them. These will be used to understand the consequences of substitutions of crucial amino acids proposed to tune the E° of the flavin, in conjunction with ab-initio calculations validated by NMR chemical shifts. Thus we will learn how specific flavin-amino acid interactions shape the reactivity of the flavin, and how interactions with the amino acids of partner proteins elicit conformational changes and modify the E°s, pKas and electronic properties of the flavins. This work will contribute to the possibility of exploiting and modifying bacterial metabolic processes to improve energy efficiency and fuel production.