The active site of ICP47, a herpes simplex virus-encoded inhibitor of the major histocompatibility complex (MHC)-encoded peptide transporter associated with antigen processing (TAP), maps to the NH2-terminal 35 residues.
The herpes simplex virus (HSV) immediate early protein ICP47 inhibits the transporter associated with antigen processing (TAP)-dependent peptide translocation. As a consequence, empty major histocompatibility complex (MHC) class I molecules are retained in the endoplasmic reticulum and recognition of HSV-infected cells by cytotoxic T lymphocytes is abolished. We chemically synthesized full-length ICP47 (sICP47) and show that sICP47 inhibits TAP-dependent peptide translocation in human cells. Its biological activity is indistinguishable from that of recombinant ICP47 (rICP47). By using synthetic peptides, we mapped the core sequence of ICP47 minimally required for TAP inhibition to residues 2-35. This segment is located within the region of the molecule conserved between ICP47 from HSV-1 and HSV-2. Through alanine scanning substitution we identified three segments within this region that are critical for the ability to inhibit TAP function. The interaction of ICP47 with TAP is unlikely to mimic precisely that of the transported peptides, as deduced from differential labeling of the TAP1 and TAP2 subunits using sICP47 fragments with chemical cross-linkers.
Galocha
B
B
Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Hill
A
A
Barnett
B C
BC
Dolan
A
A
Raimondi
A
A
Cook
R F
RF
Brunner
J
J
McGeoch
D J
DJ
Ploegh
H L
HL
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry*; D046911:Macromolecular Substances; D008285:Major Histocompatibility Complex; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D018139:Simplexvirus / Q000472:pathogenicity*; D013329:Structure-Activity Relationship; D014764:Viral Proteins
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; C105843:ICP47 protein, Herpes simplex virus; D017874:Immediate-Early Proteins; D046911:Macromolecular Substances; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; D014764:Viral Proteins