Exposing relationships using directed evolution

Functionally related protein structures that have undergone significant mutagenesis and re-arrangement over a large evolutionary time-scale might no longer share enough sequence or structural similarity to be revealed by even the most advanced database searches. Recently, Christ and Winter used directed evolution to obtain functional variants of the RNA-hairpin-binding protein Rop. Using the functional sequences obtained, a structural database search revealed previously unknown similarity to the tRNA-binding region of valyl-tRNA synthetase.