Directed Evolution with Fast and Efficient Selection Technologies

Abstract

Directed molecular evolution has proven to be a very powerful concept for the generation of proteins with improved properties, such as increased activity, binding affinity, folding efficiency or enhanced chemical and/or thermodynamic stability. We review here advances in the selection of proteins carrying desired mutations from pools of proteins that mostly carry unfavourable alterations. A short overview of the concept of directed evolution with a discussion of randomisation strategies is given first. Two technologies for the selection of proteins, each with its own advantages, are then discussed: In Ribosome Display, all steps are carried out in a cell-free system, which allows one to create very large libraries (diversity > 10¹¹), rapidly introduce mutations and thus obtain an iterative evolution. Examples with antibodies evolved for affinity or stability are discussed. In the Protein Fragment Complementation Assay, a library-versus-library selection is possible, that is, a simultaneous selection of binders against many targets. Examples with peptide and antibody libraries are discussed.