Abstract
The effects of Mg2+ ion, pH, and KCl concentration on Ca2+ binding to calmodulin were studied by using a Ca2+ ion-sensitive electrode. The Ca2+ ion affinity of calmodulin increased with increasing pH or decreasing KCl concentration. Cooperativity between the Ca2+ sites was observed, and increased with decreasing pH or increasing KCl concentration. Free Ca2+ ion concentration was decreased by adding MgCl2 ion at low Mg2+ concentration and increased at higher concentrations in the presence of small amounts of Ca2+ ion. The decrease of free Ca2+ ion concentration by Mg2+ ion strongly suggests cooperativity between the Ca2+-binding sites, and it is difficult to explain the decrease in terms of the ordered binding models previously proposed. These results can be explained by a simple model which has four equivalent binding sites that bind Ca2+ and Mg2+ competitively, and showing cooperativity when either Ca2+ or Mg2+ is bound. Mg2+ ion binding to calmodulin was measured in the presence or absence of Ca2+ to confirm the validity of this model, and no Mg2+-specific site was observed.
| Original language | English |
|---|---|
| Pages (from-to) | 1765-1772 |
| Number of pages | 8 |
| Journal | Journal of Biochemistry |
| Volume | 99 |
| Issue number | 6 |
| State | Published - Dec 1 1986 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Statistics, Probability and Uncertainty
- Applied Mathematics
- Physiology (medical)
- Radiology Nuclear Medicine and imaging
- Molecular Biology
- Biochemistry
Cite this
Calcium binding to calmodulin. cooperativity of the calcium-binding sites. / Iida, Shozo; Potter, James D.
In: Journal of Biochemistry, Vol. 99, No. 6, 01.12.1986, p. 1765-1772.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Calcium binding to calmodulin. cooperativity of the calcium-binding sites
AU - Iida, Shozo
AU - Potter, James D.
PY - 1986/12/1
Y1 - 1986/12/1
N2 - The effects of Mg2+ ion, pH, and KCl concentration on Ca2+ binding to calmodulin were studied by using a Ca2+ ion-sensitive electrode. The Ca2+ ion affinity of calmodulin increased with increasing pH or decreasing KCl concentration. Cooperativity between the Ca2+ sites was observed, and increased with decreasing pH or increasing KCl concentration. Free Ca2+ ion concentration was decreased by adding MgCl2 ion at low Mg2+ concentration and increased at higher concentrations in the presence of small amounts of Ca2+ ion. The decrease of free Ca2+ ion concentration by Mg2+ ion strongly suggests cooperativity between the Ca2+-binding sites, and it is difficult to explain the decrease in terms of the ordered binding models previously proposed. These results can be explained by a simple model which has four equivalent binding sites that bind Ca2+ and Mg2+ competitively, and showing cooperativity when either Ca2+ or Mg2+ is bound. Mg2+ ion binding to calmodulin was measured in the presence or absence of Ca2+ to confirm the validity of this model, and no Mg2+-specific site was observed.
AB - The effects of Mg2+ ion, pH, and KCl concentration on Ca2+ binding to calmodulin were studied by using a Ca2+ ion-sensitive electrode. The Ca2+ ion affinity of calmodulin increased with increasing pH or decreasing KCl concentration. Cooperativity between the Ca2+ sites was observed, and increased with decreasing pH or increasing KCl concentration. Free Ca2+ ion concentration was decreased by adding MgCl2 ion at low Mg2+ concentration and increased at higher concentrations in the presence of small amounts of Ca2+ ion. The decrease of free Ca2+ ion concentration by Mg2+ ion strongly suggests cooperativity between the Ca2+-binding sites, and it is difficult to explain the decrease in terms of the ordered binding models previously proposed. These results can be explained by a simple model which has four equivalent binding sites that bind Ca2+ and Mg2+ competitively, and showing cooperativity when either Ca2+ or Mg2+ is bound. Mg2+ ion binding to calmodulin was measured in the presence or absence of Ca2+ to confirm the validity of this model, and no Mg2+-specific site was observed.
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M3 - Article
C2 - 3091586
AN - SCOPUS:0022729955
VL - 99
SP - 1765
EP - 1772
JO - Journal of Biochemistry
JF - Journal of Biochemistry
SN - 0021-924X
IS - 6
ER -