An Escherichia coli system for evolving improved light-controlled DNA-binding proteins

Abstract

Light-switchable proteins offer numerous opportunities as tools for manipulating biological systems with exceptional degrees of spatiotemporal control. Most designed light-switchable proteins currently in use have not been optimised using the randomisation and selection/screening approaches that are widely used in other areas of protein engineering. Here we report an approach for screening light-switchable DNA-binding proteins that relies on light-dependent repression of the transcription of a fluorescent reporter. We demonstrate that the method can be used to recover a known light-switchable DNA-binding protein from a random library.