Protein splicing domains, also called inteins, have become a powerful biotechnological
tool for applications involving molecular biology and protein engineering. Early applications of inteins
focused on self-cleaving affinity tags, generation of recombinant polypeptide α-thioesters for the
production of semisynthetic proteins and backbone cyclized polypeptides. The discovery of naturallyoccurring
split-inteins has allowed the development of novel approaches for the selective modification
of proteins both in vitro and in vivo. This review gives a general introduction to protein splicing
with a focus on their role in expanding the applications of intein-based technologies in protein engineering
and chemical biology.