Lasso Proteins: Modular Design, Cellular Synthesis and Topological Transformation

Entangled proteins have attracted significant research interest. Herein, we report the first rationally designed lasso proteins, or protein [1]rotaxanes, by using p53dim entwined dimer for intramolecular entanglement and SpyTag-SpyCatcher reaction for side-chain ring closure. The lasso structures were proven by evidence from proteolytic digestion, mutation, NMR spectrometry and controlled ligation. Their dynamic properties were probed by experiments such as end-capping, proteolytic digestion, and heating/cooling. As a versatile topological intermediate, lasso proteins could be converted to rotaxanes, heterocatenanes, and "slide-ring" networks. Being entirely genetically encoded, this robust and modular lasso protein motif is a valuable addition to the topological protein repertoire and promising candidate for protein-based biomaterials.