Enhancing Enzymatic Bioconjugation Efficiency via Computer-Based Installation of a Substrate Recruitment Domain

Enzyme mediated bioconjugation provides a method for easy and rapid formation of protein-protein and protein-small molecule conjugates under mild conditions. Promiscuous enzymes are of particular interest because they can catalyze conjugation reactions on a broad set of substrates. However, this promiscuity carries the risk of undesirable off-target modifications. To mitigate this effect, we used computational design to install a substrate recruitment domain (SRD) onto the promiscuous enzyme, tyrosinase. The redesigned tyrosinase, called design42 (D42), preferentially modifies tyrosine residues adjacent to a 6-amino acid recognition motif/sequence (RS) that is bound by the SRD. Incorporation of the recognition sequence along with a neighboring tyrosine in peptides or proteins allows for rapid D42-mediated conversion of the tyrosine to an orthoquinone, which can be selectively modified with a variety of nucleophiles. We demonstrate the utility of our design system by rapidly installing cytotoxic molecules on a monoclonal antibody.