title: Three-dimensional structure of a sarcoplasmic calcium-binding protein from Nereis diversicolor.
abstract: The three-dimensional structure of a sarcoplasmic Ca2(+)-binding protein from the sandworm Nereis diversicolor has been determined at 3.0 A resolution using multiple isomorphous replacement techniques. The NH2-terminal half of the molecule contains one variant Ca2(+)-binding domain with a novel helix-loop-helix conformation and one Ca2(+)-binding domain that is no longer functional because of amino acid changes. The overall conformation of this pair of domains is different from any previously described Ca2(+)-binding protein. The COOH-terminal half of the protein contains two Ca2(+)-binding domains with the usual helix-loop-helix configuration and is similar to calmodulin and troponin C. Unlike calmodulin or troponin C, there is no exposed alpha-helix connecting the two halves of the molecule, so the overall structure is much more compact.
authors.affiliation: Department of Pathology, University of Alabama, Birmingham 35294.
authors.forename: W J
authors.initials: WJ
authors.lastname: Cook
authors.forename: S E
authors.initials: SE
authors.lastname: Ealick
authors.forename: Y S
authors.initials: YS
authors.lastname: Babu
authors.forename: J A
authors.initials: JA
authors.lastname: Cox
authors.forename: S
authors.initials: S
authors.lastname: Vijay-Kumar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000845:Annelida / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014336:Troponin / Q000737:chemistry; D019209:Troponin C; D014961:X-Ray Diffraction
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D014336:Troponin; D019209:Troponin C