Probing Changes in Ca²⁺-Induced Interaction Forces between Calmodulin and Melittin by Atomic Force Microscopy

Area of Science:

• Mechanobiology
• Biophysics
• Molecular Biology

Background:

• Mechanobiology investigates how physical forces affect biological macromolecules.
• Calmodulin (CaM) plays crucial roles in eukaryotic cellular activities.
• The biomechanical interaction between calmodulin and melittin remains underexplored.

Purpose of the Study:

• To measure the adhesion forces between calmodulin and melittin under varying calcium ion concentrations.
• To explore the biomechanical relationship of the melittin-calmodulin interaction.
• To assess the impact of calcium on melittin-calmodulin binding dynamics.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to quantify single-molecule adhesion forces.
• Experiments were conducted in phosphate-buffered saline (PBS) with gradient calcium ion (Ca2+) concentrations.
• Specific and nonspecific adhesion forces were measured between melittin and calmodulin.

Main Results:

• Baseline specific adhesion force between melittin and calmodulin was 69.4 ± 5.0 pN.
• In the presence of Ca2+ (10^-7 to 10^-3 M), specific adhesion forces increased concentration-dependently, reaching up to 213.3 ± 17.8 pN.
• Calcium ions significantly enhance the unbinding force between melittin and calmodulin.

Conclusions:

• Biomechanical studies using AFM provide insights into calcium-mediated melittin-calmodulin binding.
• Understanding these forces can inform the design and screening of calmodulin-based peptide drugs.
• The study highlights the critical role of calcium in modulating protein-protein mechanical interactions.