Erik Procko

Directed Evolution, Membrane Protein Structure and Function, Molecular Recognition, Neurotransmitters, Taste, G Protein-Coupled Receptors, HIV-1

Many proteins undergo large conformational changes as they carry out their functions. This includes receptors that shift between active and resting states, transporters that alternate access to a substrate binding site from one side of the membrane to the other, and proteins that bring two membrane together during membrane fusion. To understand protein behavior, biochemists frequently introduce mutations, perhaps to lock a receptor in an active state, or change the energy barriers between outwards and inwards facing states of a transporter. A detailed understanding of how amino acid sequence informs protein biophysical behavior can help determine protein mechanism and assist in engineering proteins with altered properties. But where should one begin? What mutations will increase protein activity? What mutations will shift the equilibria between protein conformational states?

The Procko lab has developed 'Big Data' tools for deep mutational scanning of transmembrane proteins in mammalian cells. By combining in vitro evolution with deep sequencing, it becomes possible to characterize the phenotypes of thousands of receptor mutants in a single experiment, and a comprehensive sequence-fitness landscape of a protein can be experimentally determined. Mutations can then be identified that alter protein activity, with a particular focus on finding mutations that drive proteins into specific conformations. We are currently focused on three membrane protein systems: neurotransmitter transporters associated with psychiatric disease, G protein-coupled receptors in the immune and nervous systems (including receptors for taste, chemokines and HIV-1 entry), and the HIV-1 envelope fusion protein.