title: cis-Inhibition of proteasomal degradation by viral repeats: impact of length and amino acid composition.
abstract: The Gly-Ala repeat (GAr) of the Epstein-Barr virus nuclear antigen 1 is a cis acting inhibitor of ubiquitin-proteasome proteolysis. We have investigated the capacity of various repeats to inhibit the turnover of the proteasomal substrate IkappaBalpha. Inhibition of TNFalpha-induced degradation was achieved by insertion of octamers containing three alanines or valines, interspersed by no more then three consecutive glycines. The inhibitory activity was abolished by increasing the length of the spacer, by eliminating the spacers, or by substitution of a single hydrophobic residue with a polar or charged residue. A serine containing octamer was inactive but inhibition was partially restored by insertion of three consecutive repeats. These findings suggest a model where inhibition requires the interaction of at least three alanine residues of the GAr in a beta-strand conformation with adjacent hydrophobic binding pockets of a putative receptor.
authors: Biomedicine Research and Study Center, Latvian University, Riga, Latvia.
authors: A
authors: A
authors: Sharipo
authors: M
authors: M
authors: Imreh
authors: A
authors: A
authors: Leonchiks
authors: C
authors: C
authors: Brändén
authors: M G
authors: MG
authors: Masucci
mesh_terms: D000409:Alanine / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019309:Epstein-Barr Virus Nuclear Antigens / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D005260:Female; D005998:Glycine / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D020449:Repetitive Sequences, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014452:Ubiquitins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014633:Valine / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D019309:Epstein-Barr Virus Nuclear Antigens; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; C000606204:NFKBIA protein, human; D014409:Tumor Necrosis Factor-alpha; D014452:Ubiquitins; D014764:Viral Proteins; D000072000:NF-KappaB Inhibitor alpha; D012694:Serine; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D014633:Valine; C417029:EBV-encoded nuclear antigen 1; D000409:Alanine; D005998:Glycine