title: The crystal structure of the extracellular domain of the inhibitor receptor expressed on myeloid cells IREM-1.
abstract: The immune receptors expressed on myeloid cells (IREM) are type I transmembrane proteins encoded on human chromosome 17 (17q25.1), whose function is believed to be important in controlling inflammation. To date, three IREM receptors have been identified. IREM-1 functions as an inhibitory receptor, whereas IREM-2 and IREM-3 serve an activating function. Here, we report the crystal structure of IREM-1 extracellular domain at 2.6 A resolution. The overall fold of IREM-1 resembles that of a V-type immunoglobulin domain, and reveals overall close homology with immunoglobulin domains from other immunoreceptors such as CLM-1, TREM-1, TLT-1 and NKp44. Comparing the surface electrostatic potential and hydrophobicity of IREM-1 with its murine homologous CLM-1, we observed unique structural properties for the complementary determining region of IREM-1, which suggests that they may be involved in recognition of the IREM-1 ligand. Particularly interesting is the structural conformation and physical properties of the antibody's equivalent CDR3 loop, which we show to be a structurally variable region of the molecule and therefore could be the main structural determinant for ligand discrimination and binding. In addition, the analysis of the IREM-1 structure revealed the presence of four structurally different cavities. Three of these cavities form a continuous hydrophobic groove on the IREM-1 surface, which point to a region of the molecule capable of accommodating potential ligands.
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation Polygon Scientifique, 6 Rue Jules Horowitz, 38000 Grenoble, France.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Márquez
authors.forename: Elena
authors.initials: E
authors.lastname: Galfré
authors.forename: Florine
authors.initials: F
authors.lastname: Dupeux
authors.forename: David
authors.initials: D
authors.lastname: Flot
authors.forename: Oscar
authors.initials: O
authors.lastname: Moran
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Dimasi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D000954:Antigens, Surface; C444139:CD300C protein, human; C482560:CLM-1 protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic