Fig. 2. The crystal structure of the extracellular domain of human VISTA (PDB ID: 6OIL) with several special residues highlighted. In the structure, there are six cysteines marked in yellow and an extra β-strand marked in blue. The supposed binding epitope with PSGL-1 consisting of three histidines is marked in cyan. The extra α-helix and suspected binding site with VSIG-3 consisting of four residues, two on the same helix and two on the loop, is marked in red. Among these, Arg54, Phe62, and Gln63 participate in the interaction while Arg58 is regarded as a conformation stabilizer.
