Inteins: Genetic Elements Involved in Protein Splicing

Inteins are genetic elements similar to introns which are located between the coding sequences of genes and are transcribed and translated with host proteins. Then، they remove themselves from host proteins. Inteins have been found in organisms in all three domains of life as well as viral proteins and phages. Most inteins have two domains; one is a self-splice domain and the other is a homing endonuclease (PI-SceI endonuclease) domain. Intein excision of host protein is a post translational process and is called protein splicing. It does not require auxiliary enzymes or cofactors. Flanking sequences of intein are called exteins. During protein splicing، intein is removed and the two exteins are connected by a peptide bond that forms a functional protein. This review introduces inteins as genetic elements involved in the protein splicing process.