Viral unique short region 6
This family has members such as US6 found in HCMV (Human cytomegalovirus). US6 is a unique short region glycoprotein found in the ER. It blocks the binding of ATP by TAP1 (Transporter associated with Antigen Processing 1) through a conformational change and subsequently inhibits TAP-mediated peptide translocation to the ER. It also down regulates only MHC class I. Inhibition of US6 of TAP has been shown to require residues 89 to 108 of the HCMV US6 luminal domain, whereas sequences that flank this region stabilize the binding of the viral protein to TAP. Residues 81 to 90 and the C-terminal 39 residues of HCMV US6 may also contribute to the stabilization of the interaction between US6 and TAP.
Jiyao W et al.(2023). "The conserved domain database in 2023.",