8.A.72.1.1
ICP47 protein of 88 aas with a more hydrophobic C-terminal half compared to the N-terminal half.  This protein blocks the activity of the TAP tranporter (TC# 3.A.1.209.1) preventing transport of processed foreign peptides to the ER lumen for presentation to MHC proteins (York et al. 1994). The structure of human TAP bound to ICP47 has been solved by electron cryo-microscopy (cryo-EM) to 4.0 A (Oldham et al. 2016). The structure shows that ICP47 traps TAP in an inactive conformation distinct from those of the normal transport cycle. The specificity and potency of ICP47 inhibition result from contacts between the tip of the helical hairpin and the apex of the transmembrane cavity. Thus, a clear molecular description of immune evasion by a persistent virus is available (Oldham et al. 2016).