Figure 2.

NMR studies on FimD_N. (A) Polypeptide backbone of FimD_N(25–125) represented by a bundle of 20 energy-minimized DYANA conformers. Selected positions along the polypeptide chain are identified with sequence positions. (B) Ribbon drawing of one of the 20 energy-minimized conformers. β₁–β₅ and α₁–α₂ indicate five β-strands and two α-helices, respectively. The disulfide bridge Cys63–Cys90 is drawn in yellow. The chain ends are identified by the letters N and C. (C) NMR structure of FimD_N(25–139) represented by a bundle of 20 energy-minimized DYANA conformers showing only the polypeptide backbone. The chain ends are identified by the letters N and C. The C-terminal residues 125–139 are shown in magenta. (D) Close-up view of the surface of one of the 20 energy-minimized conformers of FimD_N(25–139). Relative to (C), the structure has been rotated by approximately 90° about a vertical axis. The backbone of the C-terminal stretch 125–139 is drawn in magenta, and the side chain of Trp133 is indicated in red. Those side chains which show long-range NOE connectivities with Trp133 are drawn in bronze. In total, 14 long-range upper-distance limits between Trp133 and the rest of the protein (shown in cyan) define the position of the aromatic ring of Trp133. (E) Chemical shift variations of FimD_N upon binding to FimC–FimH_P. Δδ_Av is the weighted average of the ¹⁵N and ¹H chemical shifts, (Pellecchia et al, 1999). (F) Heteronuclear [¹⁵N,¹H]NOE measurements of FimD_N(1–139) in the FimD_N–FimC–FimH_P ternary complex. Values between 0.5 and 1 indicate well-structured parts of the protein; values<0.5 manifest increased flexibility.