title: Crystal Structure of Insulin-Regulated Aminopeptidase with Bound Substrate Analogue Provides Insight on Antigenic Epitope Precursor Recognition and Processing.
abstract: Aminopeptidases that generate antigenic peptides influence immunodominance and adaptive cytotoxic immune responses. The mechanisms that allow these enzymes to efficiently process a vast number of different long peptide substrates are poorly understood. In this work, we report the structure of insulin-regulated aminopeptidase, an enzyme that prepares antigenic epitopes for cross-presentation in dendritic cells, in complex with an antigenic peptide precursor analog. Insulin-regulated aminopeptidase is found in a semiclosed conformation with an extended internal cavity with limited access to the solvent. The N-terminal moiety of the peptide is located at the active site, positioned optimally for catalysis, whereas the C-terminal moiety of the peptide is stabilized along the extended internal cavity lodged between domains II and IV. Hydrophobic interactions and shape complementarity enhance peptide affinity beyond the catalytic site and support a limited selectivity model for antigenic peptide selection that may underlie the generation of complex immunopeptidomes.
authors.affiliation: National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece;
authors.forename: Anastasia
authors.initials: A
authors.lastname: Mpakali
authors.affiliation: National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece;
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Saridakis
authors.affiliation: Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom; and.
authors.forename: Karl
authors.initials: K
authors.lastname: Harlos
authors.affiliation: Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom; and.
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece;
authors.forename: Athanasios
authors.initials: A
authors.lastname: Papakyriakou
authors.affiliation: National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece; Department of Chemistry, University of Athens, Athens 15771, Greece.
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Kokkala
authors.affiliation: Department of Chemistry, University of Athens, Athens 15771, Greece.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Georgiadis
authors.affiliation: National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece; stratos@rrp.demokritos.gr stratikos@gmail.com.
authors.forename: Efstratios
authors.identifier: http://orcid.org/0000-0002-3566-2309
authors.initials: E
authors.lastname: Stratikos
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D020134:Catalytic Domain / Q000235:genetics; D002460:Cell Line; D018360:Crystallography, X-Ray; D010122:Cystinyl Aminopeptidase / Q000378:metabolism / Q000648:ultrastructure*; D003713:Dendritic Cells / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007313:Insecta / Q000166:cytology; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011485:Protein Binding / Q000502:physiology
chemical_list: D000941:Antigens; D000939:Epitopes; D010122:Cystinyl Aminopeptidase; C105964:leucyl-cystinyl aminopeptidase