Sequence and structural comparisons of HutZ and HugZ structural shift regions. (A) Sequence correspondence based on sequence alignment. Secondary structures are labeled above or below sequences. The shaded region represents the hypothetical β7 of HutZ, which does not exist in present crystal structure. (B) Sequence correspondence based on structure superimposition. Different from A, the four-residue-long corner of HutZ is aligned to three-residue-long corner of HugZ. Secondary structures are labeled above or below sequences. (C) Structural superimposition of HutZ and HugZ. Protein backbones are shown in trace representation with side chains in bond. (D) C-terminals of main chains of β6-2 and β9-2 point in different directions forming a 60° angle.