title: A soluble form of the first extracellular domain of mouse type 2beta corticotropin-releasing factor receptor reveals differential ligand specificity.
abstract: The heptahelical receptors for corticotropin-releasing factor (CRF), CRFR1 and CRFR2, display different specificities for CRF family ligands: CRF and urocortin I bind to CRFR1 with high affinity, whereas urocortin II and III bind to this receptor with very low affinities. In contrast, all the urocortins bind with high affinities, and CRF binds with lower affinity to CRFR2. The first extracellular domain (ECD1) of CRFR1 is important for ligand recognition. Here, we characterize a bacterially expressed soluble protein, ECD1-CRFR2beta, corresponding to the ECD1 of mouse CRFR2beta. The K(i) values for binding to ECD1-CRFR2beta are: astressin = 10.7 (5.4-21.1) nm, urocortin I = 6.4 (4.7-8.7) nm, urocortin II = 6.9 (5.8-8.3) nm, CRF = 97 (22-430) nm, urocortin III = sauvagine >200 nm. These affinities are similar to those for binding to a chimeric receptor in which the ECD1 of CRFR2beta replaces the ECD of the type 1B activin receptor (ALK4). The ECD1-CRFR2beta possesses a disulfide arrangement identical to that of the ECD1 of CRFR1, namely Cys(45)-Cys(70), Cys(60)-Cys(103), and Cys(84)-Cys(118). As determined by circular dichroism, ECD1-CRFR2beta undergoes conformational changes upon binding astressin. These data reinforce the importance of the ECD1 of CRF receptors for ligand recognition and raise the interesting possibility that different ligands having similar affinity for the full-length receptor may, nevertheless, have different affinities for microdomains of the receptor.
authors.affiliation: Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. perrin@salk.edu
authors.forename: Marilyn H
authors.initials: MH
authors.lastname: Perrin
authors.forename: Michael R
authors.initials: MR
authors.lastname: DiGruccio
authors.forename: Steven C
authors.initials: SC
authors.lastname: Koerber
authors.forename: Jean E
authors.initials: JE
authors.lastname: Rivier
authors.forename: Koichi S
authors.initials: KS
authors.lastname: Kunitake
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Bain
authors.forename: Wolfgang H
authors.initials: WH
authors.lastname: Fischer
authors.forename: Wylie W
authors.initials: WW
authors.lastname: Vale
mesh_terms: D000595:Amino Acid Sequence; D029845:Amphibian Proteins; D000818:Animals; D002942:Circular Dichroism; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D036361:Peptide Hormones; D010455:Peptides / Q000378:metabolism; D011487:Protein Conformation; D051381:Rats; D018019:Receptors, Corticotropin-Releasing Hormone / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D054832:Urocortins
chemical_list: D029845:Amphibian Proteins; C101531:CRF receptor type 2; D008024:Ligands; D010446:Peptide Fragments; D036361:Peptide Hormones; D010455:Peptides; D018019:Receptors, Corticotropin-Releasing Hormone; D011993:Recombinant Fusion Proteins; D054832:Urocortins; C518358:urocortin 2, mouse; C104416:astressin; C025727:sauvagine; D003346:Corticotropin-Releasing Hormone