Representatives of this viral protein domain are found in the vp7 capsid protein of bluetongue virus , and African horse sickness virus , the vp6 capsid protein of bovine rotavirus , and in the haemagglutinin protein of influenza virus [11867515, 9817207].
The vp7 and vp6 capsid proteins each consist of two domains, one a beta sandwich, and the other an alpha helical bundle. The beta sandwich domain described here is structurally very similar in vp6 and vp7, and may be involved in the attachment of the virus to the cell. In influenza A and B viruses, the haemagglutinin membrane glycoprotein serves to recognise the cell surface receptor sialic acid, and this domain forms the head region. In influenza C virus, a single multifunctional glycoprotein, the haemagglutinin-esterase-fusion protein, possesses a haemagglutinin domain, which recognises the cell surface receptor 9-O-acetylsialic acid, and bears strong structural resemblance to the haemagglutinin protein of influenza A and B viruses, as well as to the vp6 and vp7 capsid proteins. In each case, the domain consists of a beta-sandwich, in which the strands making up the sheets exhibit a jellyroll fold. The resultant proteins form trimers.
More information about these protein can be found at Protein of the Month: Bird Flu, Haemagglutinin.