Phage-assisted evolution of botulinum neurotoxin proteases with reprogrammed specificity

Moving targets of neurotoxins Proteases that cleave protein targets at specific sequences control many biological functions. The ability to reprogram proteases to cleave new sequences of our choosing would enable new therapeutic and biotechnological applications. Blum et al. report a laboratory evolution method to rapidly evolve proteases that cut new protein sequences and lose their ability to cut nontarget sequences (see the Perspective by Stenmark). Using this method, they evolved botulinum neurotoxin proteases, an important class of enzymes used in patients, to selectively cleave new targets, including a protein unrelated to those natively cleaved by these proteases. This work establishes a powerful approach to generate proteases with tailor-made specificities. Science , this issue p. 803 ; see also p. 782