Weak binding of divalent cations to plasma gelsolin.

Area of Science:

• Biochemistry
• Protein Chemistry

Background:

• Plasma gelsolin is a calcium-dependent protein involved in cellular processes.
• Understanding its interaction with metal ions is key to elucidating its function.

Purpose of the Study:

• To investigate the calcium binding properties of swine plasma gelsolin.
• To characterize the affinity and specificity of metal ion binding sites.
• To determine the structural consequences of metal ion binding.

Main Methods:

• Ion-exchange chromatography to assess Ca2+ binding.
• Circular dichroism spectroscopy to analyze secondary structural changes.
• Gel permeation chromatography and isoelectric focusing for further characterization.

Main Results:

• Two classes of Ca2+ binding sites were identified: high-affinity (Kd = 7 microM) and low-affinity (Kd = 1 mM).
• High-affinity sites are Ca2+-specific, while low-affinity sites can bind Mg2+.
• Ca2+ binding to high-affinity sites induces significant secondary structural changes.
• Mg2+ binding to low-affinity sites causes distinct structural alterations.
• Metal ion binding is reversible and causes minor changes in Stokes radius.

Conclusions:

• Swine plasma gelsolin undergoes significant conformational and surface charge alterations upon Ca2+ or Ca2+/Mg2+ binding.
• The distinct binding sites and their associated structural changes highlight the regulatory role of metal ions in gelsolin function.