Protein Evolution: the Theory and the Practice
Dan Tawfik

In spite the robustness and perfection of their mechanism of action, proteins posses a remarkable ability to rapidly change and adopt new functions (evolvability). Yet how proteins with new functions evolve (and sometimes, in a matter of months or years, as in drug resistance, and with enzymes that degrade man-made chemicals) is still a puzzle.
Our research aims at the laboratory reproduction of the evolution of new protein functions. In nature, cellular compartmentalization is vital for the evolution of all living organisms. Cells keep together the genes, the RNAs and proteins that they encode, and the products of their activities, thus linking genotype to phenotype. I will show how we reproduce this linkage using the aqueous compartments of water-in-oil emulsions. In each compartment, a single gene can be transcribed and translated to give many copies of the protein it encodes. Gene-libraries containing billions of variants are selected in these compartments by virtue of the linkage between the gene and the activity of the proteins it encodes.
I will describe the laboratory evolution of several new proteins, by conferring new enzymatic and inhibitory functions onto existing proteins, as well as the evolution of new protein scaffolds and topologies. I will also address some general lessons derived from these experiments as to how new proteins functions evolve, with a particular focus on the role of functional promiscuity and conformational diversity as facilitators of protein evolvability.