The structure, regulation and activity of non‐canonical inteins

Abstract

Protein splicing is the post‐translational excision of an intervening polypeptide (intein) from its flanking domains (the exteins), concomitant with extein ligation. The third step of splicing is Asn cyclization coupled to cleavage of the peptide bond linking the intein and C‐extein. Both the Methanoculleus marisnigri (Mma) and the Pyrococcus abyssi (Pab) PolII inteins promote efficient splicing with C‐terminal Gln in place of Asn. The activity of both inteins is regulated by disulfide bond formation, which might suggest a regulatory role for splicing. The Pab PolII intein splices only at elevated temperatures, allowing for isolation of a stable precursor and for study of each step of splicing in vitro. An NMR solution structure of the Pab PolII intein reveals a particularly rigid structure, a disordered loop absent in a highly similar P. horikoshii intein, and a β‐hairpin specific to inteins from archaebacteria.This material is based upon work supported by the National Science Foundation under grant MCB‐0950245 and the Camille and Henry Dreyfus Foundation.