Crystal structure of hHVEM–hLIGHT complex exhibits a 3:3 stoichiometry. (A) The analytical SEC trace of hHVEM and hLIGHT mixtures reveals a significant peak of the complex corresponding to the molecular weight ∼100 kD. The SDS-PAGE results indicate hHVEM and hLIGHT were purified to near homogeneity. Note that in the SDS gel, LIGHT trimers dissociate. RU, response units. (B and C) The hHVEM is shown as a surface, and each CRD domain is colored separately as indicated in the figure. The trimeric hLIGHT protein is shown as an orange ribbon in the figure. The side view (B) and bottom view (C) of the hHVEM–hLIGHT complex are shown. (D–F) The detailed interaction interface between hHVEM and hLIGHT. The hHVEM CRD1, CRD2, and CRD3 residues are colored as marine, hot pink, and cyan, respectively. hLIGHT residues are colored as orange. The hydrogen bonds between hHVEM and hLIGHT are indicated as dashed lines.