A gallery of GD box elements. A: GD box elements from eight different folds are shown. The unpaired hairpin is shown in red and the noncontiguous segment in gray. A structural superposition of the GD box elements is shown in the center. The structures shown are (I) 1RE9: residues 300–310, 290–292, (II) 1MQK: chain L, 11–21, 77–79, (III) 1A62: 89–99, 54–56, (IV) 1SEF: 223–233, 208–210, (V) 1YB5: 143–153, 173–175, (VI) 2DPM: 183–193, 232–235, (VII) 1V5O: 71–81, 9–11, and (VIII) 2GF6: 68–78, 11–13. B: Wall-eye and cross-eye stereo view of the superposition shown in panel A. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]