Site-Directed Modification of Yeast-Produced Proteins Using Expressed Protein Ligation

Expressed protein ligation (EPL), using non-self-cleaving inteins, allows for the site-specific addition of customized chemical moieties to the termini of proteins. In this way, protein activity can be preserved while functionalizing the target protein with a wide range of chemical handles. Here, we describe methods for EPL-based modification of proteins produced by yeast, employing an engineered, non-self-cleaving intein known as 202-08. Methods for EPL modification of both yeast surface displayed and secreted proteins with bioorthogonal chemical groups are described. These methods allow for the site-specific modification of intein-fused proteins produced in yeast.