title: 1H NMR study on amide proton exchange of calmodulin-mastoparan complex.
abstract: Amide proton exchange rates of Ca2(+)-saturated calmodulin and Ca2(+)-saturated calmodulin-mastoparan complex were studied by 1H NMR spectroscopy. Exchange rates of Gly25, Gly61, Gly98, Gly134, Ile27, Ile100, and Asn137 were determined for Ca2(+)-saturated calmodulin and for Ca2(+)-saturated calmodulin-mastoparan complex, and were found to be less than 10(-4)s-1. All these residues of which the amide proton resonances appear at lower fields were considered to form hydrogen bonds, based on the results of X-ray analysis. Exchange rates of Ile27 and Asn137 became an order of magnitude smaller when mastoparan bound to Ca2(+)-saturated calmodulin, while those of the four glycines and Ile100 did not change appreciably. The reduction in accessibility of Asn137 to water cased by mastoparan binding suggests that a part of the mastoparan binding site is probably located in or near the hydrophobic cluster of the C-terminal-half domain. The reduction in accessibility of Ile27 also suggests that another part of the mastoparan binding site is located in or near the hydrophobic cleft of the N-terminal-half domain.
authors.affiliation: Department of Polymer Science, Faculty of Science, Hokkaido University.
authors.forename: S
authors.initials: S
authors.lastname: Ohki
authors.forename: S
authors.initials: S
authors.lastname: Tsuda
authors.forename: S
authors.initials: S
authors.lastname: Joko
authors.forename: M
authors.initials: M
authors.lastname: Yazawa
authors.forename: K
authors.initials: K
authors.lastname: Yagi
authors.forename: K
authors.initials: K
authors.lastname: Hikichi
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen; D036341:Intercellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D010455:Peptides; D013329:Structure-Activity Relationship; D014862:Wasp Venoms / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D002147:Calmodulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; D014867:Water; C037500:mastoparan; D006859:Hydrogen