Herp Protein Synthesis

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Viruses have also developed methods to prevent the activity of the transporter associated with antigen processing, TAP. The TAP complex consists of two protein subunits; TAP1 and TAP2, and is an ATP-dependant peptide transporter essential for the transport of peptides to the ER and binding of the peptides to MHC class I molecules [11]. Various herpesviruses interfere with antigen presentation through the blocking the activity of TAP. The Herpes simplex virus type I (HSV-1) encodes the protein ICP47, which competes with peptides in the cytoplasm to bind to TAP. As a result fewer viral peptides are transported to the ER for loading onto MHC I molecules. This ICP47 protein consists of 88 amino acid residues, out of which residues 3-34 act as the…show more content…
The Bovine herpsvirus 1 (BoHV-1) produces the protein UL49.5, which also interferes with the transport of peptides via TAP [13]. The BoHV-1 UL49.5 interacts with the TAP core particle, through its transmembrane domain and ER-luminal domain, and prevents rearrangements in the structure of TAP. These rearrangements typically occur subsequent to the binding of antigenic peptides and ATP. Such rearrangements influence the movement of TAP, as during peptide transport the transporter molecules move slower than those not bound to peptides. However, the binding of UL49.5 hinders such changes in TAP mobility by preventing structural rearrangements, which are essential for the translocation of peptides. BoHV-1 UL49.5 also interrupts peptide transport through promoting the degradation of the TAP1 and TAP2 subunits. This is achieved by the C-terminal cytoplasmic tail of UL49.5 which connects the TAP and UL49.5 complex to ubiquitin, thereby targeting it for proteasome mediated degradation [12, 13]. This transporter is also a key target for other viral evasion proteins (Table
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