SpyTag–SpyCatcher Chemistry for Protein Bioconjugation In Vitro and Protein Topology Engineering In Vivo

The emergence of "molecular superglue," such as SpyTag-SpyCatcher chemistry, has tremendously expanded our capability in manipulating protein shape and architecture via conjugation. Telechelic proteins bearing the SpyTag and SpyCatcher reactive sequences can be expressed and purified for bioconjugation in vitro, giving protein conjugates, branched proteins, and circular proteins. By encoding both reactive sequences in the same construct for expression in vivo, the nascent protein undergoes programmed posttranslational modification guided by protein folding and reaction, leading to diverse nonlinear topologies in situ. In this chapter, we present the SpyTag-SpyCatcher chemistry as a versatile platform for protein bioconjugation and topology engineering.