title: A joint 2D NMR and theoretical investigation of Ca2+ binding loops III and IV of calmodulin.
abstract: A 2D NMR NOESY spectrum of integral CaM in water(148 residues) reveals a series of downfield-shifted crosspeaks stemming from the NH protons of the Ca2(+)-binding loops III and IV. Their attribution, with the help of already assigned proton resonances of isolated tryptic fragments, was complemented by means of energy-minimizations on the Ca2+ complexes of loops III and IV. From these calculations, a set of two alternative, related conformations was obtained for each loop. The first type of conformation provides a coordination pattern for Ca2+ that is similar to that found in loop EF of parvalbumin. The computed interproton distances in both loops are fully compatible with the inferences from the sets of NOESY cross-peaks. Evidence is also provided for interloop interactions.
authors.affiliation: Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Paris, France.
authors.forename: N
authors.initials: N
authors.lastname: Gresh
authors.forename: E
authors.initials: E
authors.lastname: Guittet
authors.forename: J Y
authors.initials: JY
authors.lastname: Lallemand
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism / Q000648:ultrastructure*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D014867:Water / Q000378:metabolism
chemical_list: D002147:Calmodulin; D014867:Water; D002118:Calcium