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Human plasma gelsolin reversibly binds Mg-ATP in Ca(2+)-sensitive manner
1Third Department of Internal Medicine, Osaka University School of Medicine.
Journal of Biochemistry
|June 1, 1992
Summary
Gelsolin binds ATP with higher affinity than GTP, but calcium ions inhibit this binding. Calcium binding induces a conformational change, disrupting the nucleotide-binding site on gelsolin.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Gelsolin is a calcium-regulated protein modulating actin dynamics in cells and plasma.
- Previous studies identified ATP binding sites on gelsolin.
Purpose of the Study:
- To investigate the nucleotide binding properties of plasma gelsolin.
- To examine the influence of divalent metal ions, particularly calcium, on gelsolin's nucleotide binding.
Main Methods:
- Affinity chromatography using immobilized Cibacron Blue F3GA.
- Equilibrium dialysis to study binding of ATP, GTP, ADP, and GDP.
- Analysis of binding in the presence of magnesium and calcium ions.
Main Results:
- Plasma gelsolin exhibits higher affinity for ATP (Kd = 2.8 x 10(-7) M) than for GTP (Kd = 1.8 x 10(-6) M).
- ADP and GDP showed negligible binding at physiological salt concentrations.
- Magnesium ions (2 mM MgCl2) supported ATP binding (Kd = 2.4 x 10(-6) M).
- Micromolar calcium concentrations inhibited ATP binding and rapidly reversed pre-formed nucleotide binding.
Conclusions:
- Gelsolin possesses specific binding sites for ATP and GTP.
- Calcium ions play a critical role in regulating gelsolin's nucleotide binding, likely through conformational changes that disrupt the binding site.