How proteins adapt: lessons from directed evolution.

Applying artificial selection to create new proteins has allowed us to explore fundamental processes of molecular evolution. These "directed evolution" experiments have shown that proteins can readily adapt to new functions or environments via simple adaptive walks involving small numbers of mutations. With the entire "fossil record" available for detailed study, these experiments have provided new insight into adaptive mechanisms and the effects of mutation and recombination. Directed evolution has also shown how mutations that are functionally neutral can set the stage for further adaptation. Watching adaptation in real time helps one to appreciate the power of the evolutionary design algorithm.