Calcium binding induces interaction between the N- and C-terminal domains of yeast calmodulin and modulates its overall conformation.
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.
Nakashima
K
K
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Ishida
H
H
Ohki
S Y
SY
Hikichi
K
K
Yazawa
M
M
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
D002147:Calmodulin; D010446:Peptide Fragments; D011994:Recombinant Proteins; D002118:Calcium