title: X-ray structure of Danio rerio secretagogin: A hexa-EF-hand calcium sensor.
abstract: Many essential physiological processes are regulated by the modulation of calcium concentration in the cell. The EF-hand proteins represent a superfamily of calcium-binding proteins involved in calcium signaling and homeostasis. Secretagogin is a hexa-EF-hand protein that is highly expressed in pancreatic islet of Langerhans and neuroendocrine cells and may play a role in the trafficking of secretory granules. We present the X-ray structure of Danio rerio secretagogin, which is 73% identical to human secretagogin, in calcium-free form at 2.1-A resolution. Secretagogin consists of the three globular domains each of which contains a pair of EF-hand motifs. The domains are arranged into a V-shaped molecule with a distinct groove formed at the interface of the domains. Comparison of the secretagogin structure with the solution structure of calcium-loaded calbindin D(28K) revealed a striking difference in the spatial arrangement of their domains, which involves approximately 180 degrees rotation of the first globular domain with respect to the module formed by the remaining domains.
authors.affiliation: Department of Biochemistry, Center for Eukaryotic Structural Genomics, University of Wisconsin-Madison, 53706-1544, USA.
authors.forename: Eduard
authors.initials: E
authors.lastname: Bitto
authors.forename: Craig A
authors.initials: CA
authors.lastname: Bingman
authors.forename: Lenka
authors.initials: L
authors.lastname: Bittova
authors.forename: Ronnie O
authors.initials: RO
authors.lastname: Frederick
authors.forename: Brian G
authors.initials: BG
authors.lastname: Fox
authors.forename: George N
authors.initials: GN
authors.lastname: Phillips
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D002478:Cells, Cultured; D018360:Crystallography, X-Ray; D020832:EF Hand Motifs; D008958:Models, Molecular; D011487:Protein Conformation; D051381:Rats; D064046:Secretagogins; D016415:Sequence Alignment; D014162:Transfection; D029961:Zebrafish Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D064046:Secretagogins; D029961:Zebrafish Proteins; C576559:scgn protein, zebrafish; D002118:Calcium