UT Chem/Biochem Dept

The 2014-2015 Beckman Scholars: Yousef Mazen Okasheh

Beckman research project in the Ellington group

Electronic control of proteins, pathways, and cells

The possibilities for specifically wiring proteins, pathways and cells are inspired both by natural and engineered interactions between cells and electrodes. A number of cells, such as Shewanella and Geobacter, can directly donate and accept electrons at electrode surfaces via extracellular cytochromes. Other cells have been interfaced with electrodes via organic molecules that act as electrochemical mediators, diffusing across membranes and carrying electrons into and out of cellular metabolism. For example, E. coli can transduce reducing equivalents from glucose into electricity via the mediator dye neutral red.

In both instances, though, the ability to directly program cellular metabolism is extremely limited, in large measure because cells cannot currently recognize electronic inputs beyond simple changes in redox potential that impact the global redox state of the cell. Within the cell, electrochemical connectivity is mediated by kinetically isolated sets of cofactors, including pools of flavins, nicotinamides, and glutathione. While the regulatory mechanisms governing these pools of cofactors are complex, the cofactors themselves cannot, for the most part, act as complex, orthogonal informational molecules to control metabolism.

To overcome the dearth of encoded eletctrochemical information within a cell, we propose to superimpose on cellular redox pools a new set of orthogonal redox molecules, organic mediators, and to thereby create an electrochemical spectra for cells that can be used for information transfer. Transcriptional and metabolic analyses of E. coli cells grown in an electrochemical cell containing different electrochemical mediators will provide unique insights into a variety of potential electrochemical interactions between mediators and the cell; for example, it is thought that neutral red can exchange electrons with fumarate reductase, but the wider range of possible interactions with metabolism, and especially with redox control of metabolism, remain unknown. By looking at differences in the genes expressed and compounds made, we anticipate identifying networks of redox active proteins and downstream signal transducers that are differentially activated. Upon identification, we will both attempt to isolate and characterize new components, and will add these components to our expanding tool kit for the modulation of cellular function by directed electronic signaling. New components can be further engineered using the same methods described above.