Fig. 1. New Ncd crystal structure. The new structure shows a large rotation of the coiled-coil stalk/neck and asymmetry of the two heads relative to the coiled coil. (A) Microtubule-binding face with the coiled coil tilted back (tubulin-interacting elements L11–α4–L12–α5, magenta; N600K, red). Neck residue N340 (green) touches motor core residue K640 (purple) in ADP-bound head H1, but the residues are separated in unstably occupied head H2. Stalk rotation occurs at G347 (gold) of H2. (B) View 180° from (A) with the coiled coil tilted forward. (C) A previous Ncd structure (PDB accession code 1CZ7) (Kozielski et al., 1999) (L11-α4-L12-α5, dark blue) with left head in same orientation as H2 of (A). (D) Side view of (A) and (C) superposed structures rotated 90° vertically, showing the ∼75° rotation of the NcdN600K coiled coil relative to the previous structure. Figure prepared using RIBBONS (Carson, 1997).