Protein splicing mechanisms and applications

Inteins are protein splicing elements that employ standard enzyme strategies to excise themselves from precursor proteins and ligate the surrounding sequences (exteins). The protein splicing pathway consists of four nucleophilic displacements directed by the intein plus the first C-extein residue. The intein active site(s) are formed by folding of the intein within the precursor, which brings together the splice junctions and internal intein residues that assist catalysis. Inteins with non-canonical catalytic residues splice by modified pathways. Understanding intein proteolytic cleavage and ligation activities has led to the development of many novel applications in the fields of protein engineering, enzymology, microarray production, target detection and activation of transgenes in plants. Recent advances include intein-mediated attachment of proteins to solid supports for microarray or western blot analysis, linking nucleic acids to proteins and controllable splicing, which converts inteins into molecular switches.