title: Identification of a novel allosteric binding site in the CXCR2 chemokine receptor.
abstract: We have shown previously that different chemical classes of small-molecule antagonists of the human chemokine CXCR2 receptor interact with distinct binding sites of the receptor. Although an intracellular binding site for diarylurea CXCR2 antagonists, such as N-(2-bromophenyl)-N'-(7-cyano-1H-benzotriazol-4-yl)urea (SB265610), and thiazolopyrimidine compounds was recently mapped by mutagenesis studies, we now report on an imidazolylpyrimidine antagonist binding pocket in the transmembrane domain of CXCR2. Using different CXCR2 orthologs, chimeric proteins, site-directed mutagenesis, and in silico modeling, we have elucidated the binding mode of this antagonist. Our in silico-guided mutagenesis studies indicate that the ligand binding cavity for imidazolylpyrimidine compounds in CXCR2 is located between transmembrane (TM) helices 3 (Phe130(3.36)), 5 (Ser217(5.44), Phe220(5.47)), and 6 (Asn268(6.52), Leu271(6.55)) and suggest that these antagonists enter CXCR2 via the TM5-TM6 interface. It is noteworthy that the same interface is postulated as the ligand entry channel in the opsin receptor and is occupied by lipid molecules in the recently solved crystal structure of the CXCR4 chemokine receptor, suggesting a general ligand entrance mechanism for nonpolar ligands to G protein-coupled receptors. The identification of a novel allosteric binding cavity in the TM domain of CXCR2, in addition to the previously identified intracellular binding site, shows the diversity in ligand recognition mechanisms by this receptor and offers new opportunities for the structure-based design of small allosteric modulators of CXCR2 in the future.
authors.affiliation: Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.
authors.forename: Petra
authors.initials: P
authors.lastname: de Kruijf
authors.forename: Herman D
authors.initials: HD
authors.lastname: Lim
authors.forename: Luc
authors.initials: L
authors.lastname: Roumen
authors.forename: Véronique A
authors.initials: VA
authors.lastname: Renjaän
authors.forename: Jiuqiao
authors.initials: J
authors.lastname: Zhao
authors.forename: Maria L
authors.initials: ML
authors.lastname: Webb
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Auld
authors.forename: Jac C H M
authors.initials: JC
authors.lastname: Wijkmans
authors.forename: Guido J R
authors.initials: GJ
authors.lastname: Zaman
authors.forename: Martine J
authors.initials: MJ
authors.lastname: Smit
authors.forename: Chris
authors.initials: C
authors.lastname: de Graaf
authors.forename: Rob
authors.initials: R
authors.lastname: Leurs
mesh_terms: D000495:Allosteric Site / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006071:Gorilla gorilla; D006801:Humans; D008024:Ligands; D008253:Macaca mulatta; D008969:Molecular Sequence Data; D002679:Pan troglodytes; D010215:Papio; D011148:Pongo pygmaeus; D023063:Receptors, Interleukin-8B / Q000235:genetics / Q000378:metabolism*; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity
chemical_list: D008024:Ligands; D023063:Receptors, Interleukin-8B; D017299:Rod Opsins