| Type: | Domain | Name: | Intein |
| Description: | Inteins, or protein introns, are parts of protein sequences that are post-translationally excised, their flanking regions (exteins) beingspliced together to yield an additional protein product [,]. Thisprocess is believed to be self-catalysed, apparently initiating at the C-terminal splice junction, where a conserved asparagine residuemediates the nucleophilic attack of the peptide bond between it and its neighbouring residue. Most inteins consist of two domains: One is involved in autocatalytic splicing, and the other is an endonucleasethat is important in the spread of inteins []. Inteins are between 134 and 608 amino acids long, and they are found in members of all three domains of life: eukaryotes, bacteria, and archaea, although most frequently in archaea. Inteinsare found in proteins with diverse functions, including metabolic enzymes, DNA and RNA polymerases, proteases, ribonucleotide reductases, and the vacuolar-type ATPase. However, enzymes involved in DNA replication and repair appear to dominate. Inteins are found in conserved regions of conserved proteins and can be regarded as parasitic genetic elements []. Inteins are difficult to identify from sequence data because they lie inthe same reading frame as the spliced protein and they are characterised by only a few short conserved motifs []: two of these are similar tothe nonapeptide LAGLIDADG, which is diagnostic of certain homing endonucleases (mutation of one such motif causes loss of endonucleicactivity, but not of the protein splicing function); another includes the C' splice site, mutations in which disable protein function. | Short Name: | INTEIN |
