Structure of the the ZU5-ANK β-spectrin binding domain. (A) Stereo diagram showing the C_α trace of ZU5-ANK. Residues are numbered corresponding to their location in the intact ankyrinR molecule. In the diagram, adjacent C_α atoms are joined by a line. (B) Ribbon stereo diagram of the ZU5-ANK subdomain in the same orientation as in panel A. The overall structure is compact and well-folded with a β-sheet–rich core and several loops. β strands are shown as arrows, helical regions as coils, and regions with no well-defined secondary structure as lines. lines. Rotating views of several representations of the molecule are shown in Video S2 (available on the Blood website; see the Supplemental Materials link at the top of the online article).