title: Calcium binding induces interaction between the N- and C-terminal domains of yeast calmodulin and modulates its overall conformation.
abstract: Calmodulin from the yeast Saccharomyces cerevisiae binds 3 mol of Ca2+ cooperatively. We report here lines of evidence supporting the intramolecular interaction between the N- and C-terminal domains which modulates the Ca2+ binding properties of yeast calmodulin. First, the sum of the Ca2+ binding curves of the N-terminal and the C-terminal half-molecule did not yield the Ca2+ binding curve of yeast calmodulin. Second, the mean residue CD of yeast calmodulin at 222 nm (-Delta epsilon222) decreased with increases in the concentration of Ca2+, whereas those of each half-molecule increased. Finally, the C2 proton of His107 in the C-terminal domain of yeast calmodulin showed three resonance peaks with increases in the concentration of Ca2+, each corresponding to the apo, the intermediate, and the Ca2+-saturated state. The intermediate peak could not be observed in the C-terminal half-molecule of yeast calmodulin. Computer simulation considering the macroscopic Ca2+ binding constants assigned this intermediate to a species consisting of the apo C-terminal domain and the N-terminal domain with at least one of the two sites occupied by Ca2+. Peptide segments spanning the defective fourth Ca2+ binding site may be involved in the interdomain interaction and the yeast-specific function of calmodulin.
authors.affiliation: Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakashima
authors.forename: H
authors.initials: H
authors.lastname: Ishida
authors.forename: S Y
authors.initials: SY
authors.lastname: Ohki
authors.forename: K
authors.initials: K
authors.lastname: Hikichi
authors.forename: M
authors.initials: M
authors.lastname: Yazawa
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D002147:Calmodulin; D010446:Peptide Fragments; D011994:Recombinant Proteins; D002118:Calcium