Figure 3. Crystal structure of the SdrE_N2N3–CFH^1206–1226 complex.

(A) Cartoon representation of the SdrE_N2N3–CFH^1206–1226 complex. N2 and N3 subdomains from the SdrE and the CFH peptide are coloured purple, green and yellow, respectively. Loop^A–B is indicated by a red arrow. Key residues involved in the side-chain interactions between SdrE and CFH are shown as sticks in the zoom-in view. Hydrogen bonds involved in the SdrE–CFH interaction are shown as black dashes. (B) GST pull-down assays of GST–CFH^1206–1226 with SdrE_N2N3 and its mutants. (C) Identification of the key residues on CFH–CCP20 for SdrE binding. Key residues are coloured red. (D) Structural comparison of apo-SdrE_N2N3 (wheat) and the SdrE_N2N3–CFH^1206–1226 complex (green). Loop^A–B and Loop^C′–D′ are circled by red dashes and labelled in black. The change of the two conformations of Loop^A–B is indicated by a red arrow. (E) A CDLL model for the SdrE–CFH interaction is shown as a cartoon.