Title: Co‐operative binding of Ca<sup>2+</sup> ions to the regulatory binding sites of gelsolin
Abstract: The rate of association of actin with gelsolin was measured at various Ca 2+ and ATP concentrations. The fraction of Ca 2+ ‐activated gelsolin was determined by quantitative evaluation of the association rates thereby assuming that Ca 2+ ‐binding gelsolin associates with actin and Ca 2+ ‐free gelsolin does not. A plot of the fraction of Ca 2+ ‐activated gelsolin vs. the free Ca 2+ concentration revealed a sigmoidal shape suggesting that co‐operative binding of Ca 2+ ions is required for activation of gelsolin. A good fit of the experimental data by calculated binding curves was obtained if two Ca 2+ ions were assumed to bind to actin in a highly co‐operative manner. ATP decreased the rate of association of gelsolin with actin and bound to gelsolin at a low affinity ( K d = 32 µ m for Ca 2+ ‐free and K d = 400 µ m for Ca 2+ ‐activated gelsolin). In contrast, a 1 : 1 gelsolin–actin complex was found to be activated for association with actin by a single Ca 2+ ion in a non‐co‐operative manner.
Publication Year: 1999
Publication Date: 1999-06-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 18
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