title: Crystal structure of the ligand binding suppressor domain of type 1 inositol 1,4,5-trisphosphate receptor.
abstract: Binding of inositol 1,4,5-trisphosphate (IP(3)) to the amino-terminal region of IP(3) receptor promotes Ca(2+) release from the endoplasmic reticulum. Within the amino terminus, the first 220 residues directly preceding the IP(3) binding core domain play a key role in IP(3) binding suppression and regulatory protein interaction. Here we present a crystal structure of the suppressor domain of the mouse type 1 IP(3) receptor at 1.8 A. Displaying a shape akin to a hammer, the suppressor region contains a Head subdomain forming the beta-trefoil fold and an Arm subdomain possessing a helix-turn-helix structure. The conserved region on the Head subdomain appeared to interact with the IP(3) binding core domain and is in close proximity to the previously proposed binding sites of Homer, RACK1, calmodulin, and CaBP1. The present study sheds light onto the mechanism underlying the receptor's sensitivity to the ligand and its communication with cellular signaling proteins.
authors.affiliation: Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, Ontario, M5G 2M9, Canada.
authors.forename: Ivan
authors.initials: I
authors.lastname: Bosanac
authors.forename: Haruka
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Toru
authors.initials: T
authors.lastname: Matsu-Ura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Michikawa
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry; D016415:Sequence Alignment
chemical_list: D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel