Metal Ion Binding in Wild-Type and Mutated Frataxin: A Stability Study

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Frataxin is crucial for iron-sulfur cluster biosynthesis.
• Cobalt (Co²⁺) is used experimentally due to iron (Fe²⁺) instability.
• Understanding frataxin stability and metal interactions is vital for disease research.

Purpose of the Study:

• To assess the stability of wild-type frataxin and cancer-associated variants upon Co²⁺ binding.
• To identify the metal-binding site within the frataxin structure.
• To elucidate the role of protein fragments and N-terminal tails in metal interaction.

Main Methods:

• Circular dichroism (CD) spectroscopy.
• Fluorescence spectroscopy.
• Differential scanning calorimetry (DSC) for melting temperature measurements.
• X-ray absorption spectroscopy (XAS) including EXAFS and XANES analysis.

Main Results:

• Co²⁺ binding induces conformational changes affecting frataxin stability.
• The acidic ridge of frataxin is identified as the primary metal-binding site.
• A longer frataxin fragment (81-210) shows reduced Co²⁺ binding compared to a shorter one (90-210).
• The N-terminal disordered tail modulates the protein's metal-binding affinity.

Conclusions:

• Frataxin stability is significantly influenced by Co²⁺ binding.
• The N-terminal tail plays a key regulatory role in frataxin's interaction with metal ions.
• Structural insights into frataxin metal binding can inform therapeutic strategies.