Design of Redox Proteins as Catalysts for Fuel Production

Redox enzymes represent a big group of proteins and they serve as catalysts for

biological processes that involve electron transfer. These proteins contain a redox center

that determines their functional properties, and hence, altering this center or incorporating

non-biological redox cofactor to proteins has been used as a means to generate redox

proteins with desirable activities for biological and chemical applications. Porphyrins and

Fe-S clusters are among the most common cofactors that biology employs for electron

transfer processes and there have been many studies on potential activities that they offer

in redox reactions.

In this dissertation, redox activity of Fe-S clusters and catalytic activity of porphyrins

have been explored with regard to protein scaffolds. In the first part, modular property of

repeat proteins along with previously established protein design principles have been

used to incorporate multiple Fe-S clusters within the repeat protein scaffold. This study is

the first example of exploiting a single scaffold to assemble a determined number of

clusters. In exploring the catalytic activity of transmetallated porphyrins, a cobalt-porphyrin

binding protein known as cytochrome c was employed in a water oxidation

photoelectrochemical cell. This system can be further coupled to a hydrogen production

electrode to achieve a full water splitting tandem cell. Finally, a cobalt-porphyrin binding

protein known as cytochrome b562 was employed to design a whole cell catalysis system,

and the activity of the surface-displayed protein for hydrogen production was explored

photochemically. This system can further be expanded for directed evolution studies and

high-throughput screening.