title: Probing the S1 specificity pocket of the aminopeptidases that generate antigenic peptides.
abstract: ERAP1 (endoplasmic reticulum aminopeptidase 1), ERAP2 and IRAP (insulin-regulated aminopeptidase) are three homologous enzymes that play critical roles in the generation of antigenic peptides. These aminopeptidases excise amino acids from N-terminally extended precursors of antigenic peptides in order to generate the correct length epitopes for binding on to MHC class I molecules. The specificity of these peptidases can affect antigenic peptide selection, but has not yet been investigated in detail. In the present study we utilized a collection of 82 fluorigenic substrates to define a detailed selectivity profile for each of the three enzymes and to probe structural and functional features of the S1 (primary specificity) pocket. Molecular modelling of the three S1 pockets reveals substrate-enzyme interactions that are critical determinants for specificity. The substrate selectivity profiles suggest that IRAP largely combines the S1 specificity of ERAP1 and ERAP2, consistent with its proposed biological function. IRAP, however, does not achieve this dual specificity by simply combining structural features of ERAP1 and ERAP2, but rather by an unique amino acid change at position 541. The results of the present study provide insights on antigenic peptide selection and may prove valuable in designing selective inhibitors or activity markers for this class of enzymes.
authors.affiliation: Protein Chemistry Laboratory, IRRP, National Centre for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece.
authors.forename: Efthalia
authors.initials: E
authors.lastname: Zervoudi
authors.forename: Athanasios
authors.initials: A
authors.lastname: Papakyriakou
authors.forename: Dimitra
authors.initials: D
authors.lastname: Georgiadou
authors.forename: Irini
authors.initials: I
authors.lastname: Evnouchidou
authors.forename: Anna
authors.initials: A
authors.lastname: Gajda
authors.forename: Marcin
authors.initials: M
authors.lastname: Poreba
authors.forename: Guy S
authors.initials: GS
authors.lastname: Salvesen
authors.forename: Marcin
authors.initials: M
authors.lastname: Drag
authors.forename: Akira
authors.initials: A
authors.lastname: Hattori
authors.forename: Luc
authors.initials: L
authors.lastname: Swevers
authors.forename: Dionisios
authors.initials: D
authors.lastname: Vourloumis
authors.forename: Efstratios
authors.initials: E
authors.lastname: Stratikos
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry* / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015778:Minor Histocompatibility Antigens; D008958:Models, Molecular; D015336:Molecular Probe Techniques; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D000939:Epitopes; C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D015778:Minor Histocompatibility Antigens; D010455:Peptides; D000626:Aminopeptidases; C464841:ERAP1 protein, human; C503944:ERAP2 protein, human