Ku and DNA-PKcs dynamic conformations

The number one in the citation hits for SAXS-study in 2010 obtained SIBYLS collaborative work on Ku and DNA-PKcs ([Hammel et al. 2010](http://www.ncbi.nlm.nih.gov/pubmed/19893054)). Here, Ku and DNA-PKcs solution structures alone and in complex with DNA, defined by X-ray scattering (SAXS), reveal major structural reorganizations that choreograph non-homologous end joining (NHEJ) initiation. These results show how protein and DNA interactions initiate large Ku and DNA-PKcs rearrangements to control DNA-PK biological functions as a macromolecular machine orchestrating assembly and disassembly of the initial NHEJ complex on DNA.

The figure shows The averaged SAXS envelopes for DNA-PKcs (gray) and phosphorylated DNA-PKcs (orange) each with the crystal structure superimposed, plus representative single SAXS envelope (top) revealing the large conformational change resulting from phosphorylation. The enclosed cavity in the head region, observed in the crystal structure, is seen visible in the SAXS data as highlighted by darker shading.