Intein

An intein is a segment of a protein that is able to excise itself and join the remaining portions (the exteins) with a peptide bond in a process termed protein splicing. Inteins have also been called "protein introns".

Intein-mediated protein splicing occurs after the intein-containing mRNA has been translated into a protein. This precursor protein contains three segments — an N-extein followed by the intein followed by a C-extein. After splicing has taken place, the resulting protein contains the N-extein linked to the C-extein; this splicing product is also termed an extein.