CD155 is a protein that in humans is encoded by CD155 gene. CD155 is a type I transmembrane glycoprotein in the immunoglobulin superfamily. CD155 is a transmembrane protein with 3 extracellular immunoglobulin-like domains, D1-D3, where D1 is recognized by the virus. Low resolution structures of CD155 complex have been obtained using electron microscopy while a high resolution structures of the ectodomain D1 and D2 of CD155 are solved by x-ray crystallography.