This domain is found in several Herpes viruses glycoproteins. This is a family includes glycoprotein-D (gD or gIV) which is common to herpes simplex virus types 1 and 2, as well as equine herpes, bovine herpes and Marek's disease virus. Glycoprotein-D has been found on the viral envelope and the plasma membrane of infected cells. and gD immunisation can produce an immune response to bovine herpes virus (BHV-1). This response is stronger than that of the other major glycoproteins gB (gI) and gC (gIII) in BHV-1. Glycoprotein G (gG)is one of the seven external glycoproteins of HSV1 and HSV2. This family also contains the glycoprotein GX, (gX), initially identified in Pseudorabies virus.