Protein Domain : DNA-dependent protein kinase catalytic subunit, CC5 IPR045581

Type	Domain
Description	This entry represents the C-terminal region of the Circular Cradle segment (CC) of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), containing most of the supersecondary structure CC4 and the complete CC5. Structural studies revealed that this domain contains the Ku-binding site B and one of the caspase-3 cleavage sites [ ].DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is involved in DNA nonhomologous end joining (NHEJ), which is recruited by Ku70/80 heterodimer to DNA ends and required for double-strand break (DSB) repair. DNA-PKcs phosphorylates a number of protein substrates, including the heat shock protein 90 (HSP90), the transcription factors p53, specificity protein 1 (Sp1) and MYC23, and a majority of NHEJ factors. It folds into three well-defined large structural units, consisting of a N-terminal region (arranged in four supersecondary α-helical structures, N1 to N4), the Circular Cradle (consisting of five supersecondary α-helical structures CC1 to CC5), and the C-terminal Head (comprising FAT, FRB, kinase, and FATC). The N-terminal and CCs regions resemble HEAT repeats, and thus, they are also referred to as N-HEAT and M-HEAT ('middle'), respectively. The N-terminal region likely mediates DNA binding and, together with the CCs, forms a ring through which Ku70/80 may present DNA for repair. The CCs form a curved elliptical ring that serves as a scaffold to maintain the integrity of the whole complex. It has been suggested that the binding of Ku or DNA activates the allosteric mechanism required for communication between the N terminus and the CC with the kinase in the Head [ , , , ].
Short Name	DNAPKcs_CC5