title: Solution structure of calmodulin-W-7 complex: the basis of diversity in molecular recognition.
abstract: The solution structure of calcium-bound calmodulin (CaM) complexed with an antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), has been determined by multidimensional NMR spectroscopy. The structure consists of one molecule of W-7 binding to each of the two domains of CaM. In each domain, the W-7 chloronaphthalene ring interacts with four methionine methyl groups and other aliphatic or aromatic side-chains in a deep hydrophobic pocket, the site responsible for CaM binding to CaM-dependent enzymes such as myosin light chain kinases (MLCKs) and CaM kinase II. This competitive binding at the same site between W-7 and CaM-dependent enzymes suggests the mechanism by which W-7 inhibits CaM to activate the enzymes. The orientation of the W-7 naphthalene ring in the N-terminal pocket is rotated approximately 40 degrees with respect to that in the C-terminal pocket. The W-7 ring orientation differs significantly from the Trp800 indole ring of smooth muscle MLCK bound to the C-terminal pocket and the phenothiazine ring of trifluoperazine bound to the N or C-terminal pocket. These comparative structural analyses demonstrate that the two hydrophobic pockets of CaM can accommodate a variety of bulky aromatic rings, which provides a plausible structural basis for the diversity in CaM-mediated molecular recognition.
authors.affiliation: Molecular Chemistry Research Chemistry Laboratories, Yamanouchi Pharmaceutical Co., Tsukuba, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Osawa
authors.forename: M B
authors.initials: MB
authors.lastname: Swindells
authors.forename: J
authors.initials: J
authors.lastname: Tanikawa
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Mase
authors.forename: T
authors.initials: T
authors.lastname: Furuya
authors.forename: M
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000818:Animals; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D013449:Sulfonamides / Q000737:chemistry* / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D002147:Calmodulin; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D012996:Solutions; D013449:Sulfonamides; C017967:W 7