Fig. 3: Structure of T. brucei ISG65G receptor bound to complex C3d.
From: Invariant surface glycoprotein 65 of Trypanosoma brucei is a complement C3 receptor
a The structure of ISG65 in complex with C3d. The helices of ISG65 are each coloured differently, with core helices 1, 2, and 4 shown in light green, turquoise, and blue, while shorter ISG65 helices 3 and 5 are shown in light grey and dark grey. All helices are labelled H1–H5. C3d is shown in orange, with the location of the thioester bond-forming cysteine highlighted black. N and C indicate the termini of ISG65. b A schematic showing the features of ISG65. The location of helices 1–5 are shown, using the same colours as a, while the transmembrane helix, predicted using TMHMM, is light grey. Green bars show regions of ISG65 that were resolved in the crystal structure, and red bars show regions predicted to be disordered by AUCpreD65. The three loops in between helices, which are largely unresolved, are labelled L1–L3. c Comparison of the structure of ISG65 with equivalent views of the T. brucei factor H receptor, FHR22, the transferrin receptor, TfR17 and the haptoglobin-haemoglobin receptor, HpHbR20. d Different views of the ISG65 structure with helix 1 (light green), helix 2 (turquoise), and helix 3 (blue) highlighted to show the kinks that give rise to the curved structure of ISG65. The angles of each kink were measured using Chimera66,67, and are indicated in black.
