Biomolecular Click Reactions Using a Minimal pH-Activated Catcher/Tag Pair for Producing Native-Sized Spider-Silk Proteins

A type of protein/peptide pair known as Catcher/Tag pair spontaneously forms an intermolecular isopeptide bond which can be applied for biomolecular click reactions. Covalent protein conjugation using Catcher/Tag pairs has turned out to be a valuable tool in biotechnology and biomedicines, but it is essential to increase the current toolbox of orthogonal Catcher/Tag pairs to expand the range of applications further, for example, for controlled multiple-fragment ligation. We report here the engineering of novel Catcher/Tag pairs for protein ligation, aided by a crystal structure of a minimal CnaB domain from Lactobacillus plantarum. We show that a newly engineered pair, called SilkCatcher/Tag enables efficient pH-inducible protein ligation in addition to being compatible with the widely used SpyCatcher/Tag pair. Finally, we demonstrate the use of the SilkCatcher/Tag pair in the production of native-sized highly repetitive spider-silk-like proteins with >90 % purity, which is not possible by traditional recombinant production methods.

Automated summary

A type of protein/peptide pair called Catcher/Tag can spontaneously form an intermolecular isopeptide bond for biomolecular click reactions. Increasing the toolbox of orthogonal Catcher/Tag pairs is crucial to expand their applications, such as controlled multiple-fragment ligation. This study reports the engineering of novel Catcher/Tag pairs, including SilkCatcher/Tag, which enables pH-inducible protein ligation and is compatible with the widely used SpyCatcher/Tag pair. The SilkCatcher/Tag pair is also shown to be useful in producing native-sized highly repetitive spider-silk-like proteins with >90% purity, which is not achievable by traditional recombinant production methods.