Structural and biochemical analysis of a novel atypically split intein reveals a conserved histidine specific to cysteine-less inteins.

Protein -splicing mediated by a split intein reconstitutes a protein backbone from two parts. This virtually traceless autoprocessive reaction provides the basis for numerous protein engineering applications. Protein splicing typically proceeds through two thioester or oxyester intermediates involving the side chains of cysteine or serine/threonine residues.