Protein splicing is post-translational process for the excision of intervening sequences that interrupt the coding sequences of certain genes. To intervening sequence is transcribed into mRNA and translated into a nonfunctional protein precursor, which than undergoes a self-catalyzed rearrangement in which the intervening polypeptide segment, known as intein, is excised and the flanking protein segments, the exteins, are concomitantly joined to yield the mature protein, which is the functional product of the interrupted gene.

The study of the mechanism of protein splicing has uncovered an exceedingly complex self-catalyzed process that requires neither exogenous cofactors nor auxiliary enzymes or energy sources such as adenosine triphosphate (ATP) or guanosine triphosphate (GTP).

This figure gives a schematic representation of protein splicing.