Calcium binding to calmodulin. cooperativity of the calcium-binding sites

Shozo Iida, James D. Potter

Research output: Contribution to journalArticle

42 Citations (Scopus)

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 languageEnglish
Pages (from-to)1765-1772
Number of pages8
JournalJournal of Biochemistry
Volume99
Issue number6
StatePublished - Dec 1 1986
Externally publishedYes

Fingerprint

Calmodulin
Binding sites
Calcium
Binding Sites
Ions
Ion-Selective Electrodes
Magnesium Chloride
Decrease
Affine transformation
Electrode

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 journalArticle

Iida, Shozo ; Potter, James D. / Calcium binding to calmodulin. cooperativity of the calcium-binding sites. In: Journal of Biochemistry. 1986 ; Vol. 99, No. 6. pp. 1765-1772.
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