The 2018 Nobel Prize in Chemistry was awarded to Frances H. Arnold of California Institute of Technology for the directed evolution of enzymes and to George P. Smith of the University of Missouri and Gregory P. Winter of the MRC Laboratory of Molecular Biology for the phage display of peptides and antibodies. Arnold will receive half of the approximately $1 million prize; Smith and Winter will split the other half equally.
This year’s prize “recognizes the power of harnessing protein evolution to solve a wide range of problems in the molecular sciences,” says David R. Liu of Harvard University, who has developed a version of directed evolution called phage-assisted continuous evolution. “My hat’s off to Smith, Winter, and Arnold for their contributions to this multidisciplinary field that beautifully integrates chemistry, molecular biology, and protein science.”
Directed evolution is an iterative lab method involving mutation and screening that speeds up the natural selection process through which life on Earth evolved. In Arnold’s technique, she introduces random mutations into the gene for a starting enzyme, expresses the variant genes in bacteria, and screens the mutated enzymes produced by the microbes for desired activity. By repeating this process with the best performers, researchers can find proteins with the desired enzymatic properties in terms of activity, binding affinity, or specificity.
Arnold conducted the first directed evolution of enzymes in 1993. In that work, she evolved a version of the enzyme subtilisin E that was active at high concentrations of the polar organic solvent dimethylformamide. Four rounds of mutagenesis and screening resulted in an enzyme that was 256 times as active as the original enzyme.
Smith reported the original phage display method in 1985. In this library-based method for screening for proteins that bind a specific molecule, the gene for each member of the library is inserted in the DNA for coat protein III of phage, a virus that infects bacteria. The phage infects and reproduces in bacteria. Scientists can then use the target molecule as bait to enrich phages released by the bacteria that have the binding protein of interest on their surface.
Sequencing the genetic material of the collected phages yields genes for proteins with desired binding affinity.
Winter extended phage display to screening for novel antibodies. In 1990, Winter’s team reported the phage display of a folded and fully functional antibody fragment called a single-chain variable fragment. This first demonstration identified selective antibodies that could bind hen egg-white lysozyme but not human lysozyme or turkey egg-white lysozyme.
Directed evolution and phage display have both become widely used methods. C&EN featured Provivi, a company founded by Arnold and two of her coworkers, in its 10 Start-ups to Watch in 2015. Provivi uses enzymes developed through directed evolution to make insect pheromones for pest control. And researchers have used phage display to identify antibodies with high binding affinity for use as pharmaceuticals. The first approved drug developed using phage display is Abbvie’s Humira (adalimumab), which was approved by the U.S. Food & Drug Administration in 2002.
“This is a fantastic award that recognizes how laboratory evolution, in a few short decades, has revolutionized our ability to tailor the properties of biomolecules for applications unimagined in nature,” says Donald Hilvert, an expert in directed evolution at the Swiss Federal Institute of Technology, Zurich.
Commenting on the biological flavor of this year’s chemistry Nobel, Peter K. Dorhout, president of the American Chemical Society, says, “This is chemistry. Chemistry is broad and deep. In the case of evolved enzymes, it’s catalytic chemistry and organic chemistry. To develop and understand the critical tools to evaluate how cells behave is also fundamental analytical chemistry.”
UPDATE: This story was updated on Oct. 8, 2018, to correct the method that David R. Liu developed. It's phage-assisted continuous evolution, not phage-assisted directed evolution.