anteins

Anteins are protein segments that can excise themselves from a precursor protein and ligate the flanking sequences together. This process, known as protein splicing, is a post-translational modification. Anteins are found in a variety of organisms, including bacteria, archaea, fungi, and some eukaryotes. They are often found as part of larger intein proteins, where the antein is the self-splicing catalytic domain.

The mechanism of protein splicing involves a series of transesterification and cyclization reactions. The N-terminal flanking sequence, called the extein, remains attached to the N-terminal part of the intein. Similarly, the C-terminal extein is attached to the C-terminal part of the intein. The intein then undergoes a complex series of internal rearrangements, leading to the cleavage of the peptide bonds connecting it to the exteins and the formation of a new peptide bond between the two exteins. The intein itself is released as a separate cyclic or linear peptide.

Protein splicing can occur in cis, meaning the intein and exteins are part of the same polypeptide chain, or in trans, where the N-terminal and C-terminal halves of the intein are encoded on separate genes or polypeptide chains but still associate and catalyze the splicing reaction. This trans-splicing capability has made inteins valuable tools in protein engineering for applications such as protein purification, protein ligation, and the production of specific protein fragments. The discovery and characterization of anteins and their splicing mechanism have significantly advanced our understanding of protein maturation and provided novel biotechnological applications.