Figure 3.

X-ray structure of the ternary FimD_N(1–125)–FimC–FimH_P complex. (A) Ribbon diagram of the ternary complex, with FimD_N(1–125) depicted in green, FimC in cyan and the pilin domain FimH_P in yellow. The G₁ donor strand of FimC is colored in blue. A black dashed line indicates residues 10–18 of FimD_N, for which no electron density was observed. The N- and C-termini of FimD_N are labeled in green. (B) Close-up view of the hydrophobic contacts between Phe8 of the N-terminal FimD_N tail (green) and residues from FimC (cyan) and FimH_P (yellow). The final 2mFo−DFc electron density map is contoured at 1σ level. (C) Stereo representation of the tail interface. Residues from FimD_N, in stick model, are shown in green. The molecular surfaces of FimC (slate-grey) and FimH_P (light yellow) are shown in semitransparent mode. Residues contributing to the FimC and FimH_P surfaces and interacting with FimD_N are shown in more intense color: cyan for FimC and yellow for FimH_P residues, respectively. Residues from the G₁ donor strand of FimC contributing to the molecular surface appear in blue. (D) Stereo representation of the interface between FimC and the folded FimD_N core 25–125. Some hydrogen bonds between FimC and the FimD_N core are depicted as thin dashed lines. Color coding is as in (A). The figure was prepared with Pymol (www.pymol.org).