Structure of PECAM_659-711 in the presence of DPC. (A) Cα backbone trace representation of the NMR ensemble of 20 structures superimposed over residues 682-701. Unstructured residues 659-679 and 706-711 are not shown for clarity. (B) Helical wheel diagram illustrating the amphipathic nature of the DPC-stabilized structure. Hydrophobic (white circles), polar (gray circles), and charged (gray polygons) residues are labeled by amino acid type and number. (C) One-dimensional ¹H slices from aromatic ¹H-¹³C HSQC spectra of PECAM_659-711 in the presence of DPC show that addition of 0.5mM Mn²⁺ induces broadening of the resonance of the histidine (H₆₇₄) side chain, which is located outside the membrane-interacting region (i), but not of the tyrosine (Y₆₈₆/Y₇₀₁) side chains, which are located within the membrane-interacting region (ii).