title: Cryo-EM structure of the DNA-dependent protein kinase catalytic subunit at subnanometer resolution reveals alpha helices and insight into DNA binding.
abstract: The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) regulates the nonhomologous end joining pathway for repair of double-stranded DNA (dsDNA) breaks. Here, we present a 7A resolution structure of DNA-PKcs determined by cryo-electron microscopy single-particle reconstruction. This structure is composed of density rods throughout the molecule that are indicative of alpha helices and reveals structural features not observed in lower resolution EM structures. Docking of homology models into the DNA-PKcs structure demonstrates that up to eight helical HEAT repeat motifs fit well within the density. Surprisingly, models for the kinase domain can be docked into either the crown or base of the molecule at this resolution, although real space refinement suggests that the base location is the best fit. We propose a model for the interaction of DNA with DNA-PKcs in which one turn of dsDNA enters the central channel and interacts with a resolved alpha-helical protrusion.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: Dewight R
authors.initials: DR
authors.lastname: Williams
authors.forename: Kyung-Jong
authors.initials: KJ
authors.lastname: Lee
authors.forename: Jian
authors.initials: J
authors.lastname: Shi
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
authors.forename: Phoebe L
authors.initials: PL
authors.lastname: Stewart
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D004247:DNA / Q000378:metabolism*; D051747:DNA-Activated Protein Kinase / Q000737:chemistry* / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D004247:DNA; D051747:DNA-Activated Protein Kinase