Conserved region amino acid mutations in Calcin: Altering the RyR structural-functional relationship

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Calcin peptides from scorpion venom bind Ryanodine Receptors (RyRs), modulating calcium release.
• Previous studies indicated electrostatic interactions are key, but charge-reversal effects were unknown.

Purpose of the Study:

• To investigate the impact of charge-reversal mutations (E12R, E12K, E29R, E29K) in OpiCa1 on its structure, RyR binding, and function.
• To explore structure-function relationships for optimizing Calcin-based therapeutics.

Main Methods:

• Computational modeling (molecular docking and dynamics simulations) to predict binding modes and stability.
• Experimental validation using cellular assays to measure calcium (Ca2+) release in cardiomyocytes.

Main Results:

• All OpiCa1 mutants retained the native inhibitor cystine knot fold but showed altered surface electrostatics.
• Simulations predicted distinct binding interactions with RyR1 and RyR2 for each mutant.
• The E29R mutant demonstrated significantly enhanced Ca2+ release from cardiomyocytes via RyR2 activation compared to wild-type.

Conclusions:

• Residue E29 is critical; charge-reversal mutation to arginine (E29R) optimizes Calcin activity by improving electrostatic complementarity with RyR.
• This provides a rational strategy for developing enhanced peptide therapeutics for calcium dysregulation diseases targeting RyRs.