Fig. 5.

Models for arrangement of β-strands formed by residues 32–40 into antiparallel β-sheets. Ribbons represent β-strands and spheres represent atoms with NMR-derived structural constraints described in the text. In Panels A–C, spheres are color coded by residue as marked in Panel C. The red spheres, for example, represent carbonyl carbon atoms on V36, for which PITHIRDS-CT data indicate a close interatomic proximity.²³ A) An antiparallel β-sheet composed only of equivalent β-strands (residues 32–40). B) An antiparallel β-sheet composed of β-hairpins with two nonequivalent β-strands (gray ribbons for residues 32–40 and blue ribbons for a presently unconstrained N-terminal β-strand). C) A three-fold symmetric configuration of antiparallel β-strands. D) An enlarged view of the peptide backbone regions defined by the dashed boxes in Panels (A) and (B) with side chains deleted. Experimentally constrained interatomic distances are indicated by arrows. In Panels D and E, atoms are colored by element (C: black; H: white; N: blue; O: red). (E) An enlarged view of the peptide backbones within the dashed box in Panel C, with constrained inter-atomic distances indicated by arrows.