<p>DNA repair of double-stranded breaks by non-homologous end joining (NHEJ) is accomplished by a two-protein system that is present in a minority of prokaryotes. One component is the Ku protein (see <db_xref db="INTERPRO" dbkey="IPR009187"/>), which binds DNA ends. The other is a DNA ligase, a protein that is a multidomain polypeptide in most of those bacteria that have NHEJ, a permuted polypeptide in <taxon tax_id="1773">Mycobacterium tuberculosis</taxon> and a few other species, and the product of tandem genes in some other bacteria. This region represents the central ligase domain.</p> DNA polymerase LigD, ligase domain