C. Close-up views of the DCX binding site focusing on loop 3 density, which differentiates DC domains. Refined atomic models in predominantly backbone representation are fitted to their respective density maps (wireframe). Selected residues are labelled with single letter codes and selected side chains are shown as sticks. Nucleotide in tubulin subunit designated as β1 is shown as sticks in the top left corner of each panel. Colours as in (B), or oxygen atom, red; nitrogen atom, navy blue. 