The RTP site shared by the HIV-1 Tat protein and the 11S regulator subunit alpha is crucial for their effects on proteasome function including antigen processing.
The human immunodeficiency virus-1 Tat protein inhibits the peptidase activity of the 20S proteasome and competes with the 11S regulator/PA28 for binding to the 20S proteasome. Structural comparison revealed a common site in the Tat protein and the 11S regulator alpha-subunit (REGalpha) called the REG/Tat-proteasome-binding (RTP) site. Kinetic assays found amino acid residues Lys51, Arg52 and Asp67 forming the RTP site of Tat to be responsible for the effects on proteasomes in vitro. The RTP site identified in REGalpha consists of the residues Glu235, Lys236 and Lys239. Mutation of the REGalpha amino acid residues Glu235 and Lys236 to Ala resulted in an REGalpha mutant that lost the ability to activate the 20S proteasome even though it still forms complexes with REGbeta and binds to the 20S proteasome. The REGalpha RTP site is needed to enhance the presentation of a cytomegalovirus pp89 protein-derived epitope by MHC class I molecules in mouse fibroblasts. Cell experiments demonstrate that the Tat amino acid residues 37-72 are necessary for the interaction of the viral protein with proteasomes in vivo. Full-length Tat and the Tat peptide 37-72 suppressed 11S regulator-mediated presentation of the pp89 epitope. In contrast, the Tat peptide 37-72 with mutations of amino acid residues Lys51, Arg52 and Asp67 to Ala was not able to reduce antigen presentation.
Huang
Xiaohua
X
Division of Molecular Biology, Department of Surgery, Medical Faculty Charité, Humboldt University, Monbijoustr. 2A, Berlin, Germany.
Seifert
Ulrike
U
Salzmann
Ulrike
U
Henklein
Peter
P
Preissner
Robert
R
Henke
Wolfgang
W
Sijts
Alice J
AJ
Kloetzel
Peter Michael
PM
Dubiel
Wolfgang
W
D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D001120:Arginine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D001324:Autoantigens; D001667:Binding, Competitive; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003587:Cytomegalovirus / Q000276:immunology; D004789:Enzyme Activation; D000939:Epitopes / Q000276:immunology; D015696:Gene Products, tat / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000737:chemistry*; D006801:Humans; D008239:Lysine / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D009124:Muscle Proteins; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D021122:Protein Subunits; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D054322:tat Gene Products, Human Immunodeficiency Virus
D001324:Autoantigens; D000939:Epitopes; D015696:Gene Products, tat; C099558:Ki antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; C085047:PSME1 protein, human; D010446:Peptide Fragments; D021122:Protein Subunits; D011506:Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D001224:Aspartic Acid; D001120:Arginine; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine