The Ku heterodimer (composed of Ku70 Swiss:P12956 and Ku80 Swiss:P13010) contributes to genomic integrity through its ability to bind DNA double-strand breaks and facilitate repair by the non-homologous end-joining pathway. This is the C terminal arm. This alpha helical region embraces the beta-barrel domain Pfam:PF02735 of the opposite subunit [1].

1: Structure of the Ku heterodimer bound to DNA and its implications for double-strand break repair. Walker JR, Corpina RA, Goldberg J; Nature 2001;412:607-614. PMID:11493912

2: Prokaryotic homologs of the eukaryotic DNA-end-binding protein Ku, novel domains in the Ku protein and prediction of a prokaryotic double-strand break repair system. Aravind L, Koonin EV; Genome Res 2001;11:1365-1374. PMID:11483577