Inteins and Their Use in Protein Synthesis with Fungi

Abstract

Inteins are internal protein elements that auto-catalyze their excision from a precursor protein and the ligation of the flanking sequences (exteins) with a peptide bond. This post-translational process is called cis protein splicing and involves only four intramolecular reactions, and a small number of key catalytic residues in the intein and exteins, but no external factor or energy. Protein-splicing can also occur in trans when inteins are encoded by two separated genes and synthesized as N- and C-terminal domains together with joined exteins. Over the past two decades intein-encoding organisms have been identified in all three domains of life and viral genomes. In eukaryotes, they have been only found in fungi and algae. The discovery of protein-splicing led to the development of several intein-based protein-engineering applications, such as protein purification, modification, ligation, cyclization and conditional protein splicing.