A phenomenon (known to occur in yeast, bacteria, and archaeons) during which a precursor protein has a segment excised from it and the N- and C-terminal fragments are subsequently spliced together. The excised segment is called an intein (internal pro tein sequence), and the spliced protein is composed of N- and C- exteins (external pro tein sequence). An intein cuts itself from its parent molecule and unites its former neighboring exteins with the usual peptide bond. Introns (q.v.) often encode a “homing endonuclease” (q.v.) that can excise a DNA segment, allowing it to move to a new genomic location. Analogously, many inteins contain a “homing endonuclease” segment in addition to a protein splicing region. This kind of intein can excise the DNA that encodes it out of a gene and allow the DNA to be transported elsewhere. A DNA polymerase in Synechocystis (q.v.) is encoded by two gene segments sandwiched between several other genes. Each segment terminates in half of an intein gene (a “split intein”). When their protein products make contact, the intein reassembles itself and splices the two polymerase segments together. Compare with fused protein, fusion gene. See Chronology, 1990, Kane et al.; 1997, Klenk et al.; posttranslational processing.
Subjects: Genetics and Genomics.