title: Natural peptides selected by diabetogenic DQ8 and murine I-A(g7) molecules show common sequence specificity.
abstract: In this study, a large number of naturally processed peptides was isolated and identified from the human diabetes-susceptible class II MHC molecules HLA-DQ8 (DQA1*0301,DQB1*0302) and from murine I-A species, both of which are expressed in genetically identical APC lines. The peptides presented during the processing of autologous proteins were highly selective in showing sequence specificity, mainly consisting of 1 or more acidic residues at their C terminus. Testing for binding to the MHC molecules revealed that the position 9 (P9) acidic residues of the peptides contributed decisively to binding. For HLA-DQ8, the P1 residue, which was also an acidic amino acid, influenced binding positively. Both HLA-DQ8 and I-A(g7) selected for common peptides that bound in the same register. There was no evidence for selection of peptides having nonspecific or promiscuous binding. Thus, diabetogenic class II MHC molecules are highly selective in terms of the peptides presented by their APCs, and this is governed by the features of their P9 anchor pocket. These results are in striking contrast to those from studies examining synthetic peptide or phage display libraries, in which many peptides were shown to bind.
authors.affiliation: Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Anish
authors.initials: A
authors.lastname: Suri
authors.forename: James J
authors.initials: JJ
authors.lastname: Walters
authors.forename: Michael L
authors.initials: ML
authors.lastname: Gross
authors.forename: Emil R
authors.initials: ER
authors.lastname: Unanue
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000938:Antigen-Presenting Cells; D001324:Autoantigens / Q000276:immunology*; D002460:Cell Line; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D006683:HLA-DQ Antigens / Q000276:immunology*; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides; D011485:Protein Binding / Q000276:immunology
chemical_list: D001324:Autoantigens; D006683:HLA-DQ Antigens; C109756:HLA-DQ8 antigen; D019151:Peptide Library; D010455:Peptides