Ankyrin repeats in context with human population variation
Fig 7
Hydrogen bonding patterns of the two Asx motifs found in the ANK and their location within the ARD.
Only repeats with either Asn or Asp at these positions will present this hydrogen bonding pattern. (A) Asx-β-turn at positions 27–30. Conserved Asx, i.e., Asp/Asn, side chain at position i = 27 forms an extra hydrogen bond with backbone N at position i + 2; (B) Type 1 β-bulge loop with Asx motif at positions 32–3. Conserved Asx side chain at domain position i = 32 forms two hydrogen bonds with backbone N of residues i + 2 and i + 4. The rest of the hydrogen bonds originate from the backbone of the residues and are not specific of Asx motifs. PDB: 5MA3 [14]; (C) DARPin-8.4 (Barandun J, Schroeder T, Mittl PRE, Grutter MG) PDB: 2Y1L. Light blue lines represent the hydrogen bonds that determine these secondary structure motifs. The conservation of the Asx residues at positions 27 and 32, and the hydrogen bonding network they facilitate, suggest that these Asx motifs are one of the most structurally important components of the ankyrin repeat domain structure. Figure obtained with UCSF Chimera [7].