Overall structure of the hHVEM–hLIGHT complex and the binding interface between hHVEM and hLIGHT. (A and B) One asymmetry unit contains six independent chains of hLIGHT (cyan and yellow cartoon) and six independent chains of hHVEM (blue and red cartoon) forming two independent 3:3 hHVEM–hLIGHT complexes. Each chain is labeled in the figure. (A) Side view of the two hHVEM–hLIGHT complexes in one asymmetry unit. (B) Side view of the superimposition result of the two hHVEM–hLIGHT complexes. (C) The overall structure of the hHVEM–hLIGHT complex (top left) and magnified view of one copy hHVEM binding to two adjacent hLIGHT monomers (bottom right). hLIGHT is shown as an orange cartoon. hHVEM is presented as gray cartoon for one copy and a CRD colored surface for two copies. (D) Magnified views of the binding interface between hHVEM and hLIGHT. The residues from the “upper” region of the hHVEM–hLIGHT complex are shown as marine color sticks on the top left panel. The residues from the AA″ and GH loops part of the “lower” region of the hHVEM–hLIGHT interface are shown as cyan sticks on the top right and bottom right panels. The residues from the DE loop part of the lower region of the hHVEM–hLIGHT interface are shown as magenta sticks on bottom left panel. The residues of hHVEM contributing to the interface are presented as gray sticks. Shown are the interaction interface of the “upper” region between hLIGHT and hHVEM (top left panel), the interaction interface between the GH loop of hLIGHT and hHVEM (top right panel), the interaction interface between the DE loop of hLIGHT and hHVEM (bottom left panel), and the interaction interface between the AA′ loop of hLIGHT and hHVEM (bottom right panel).