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The B22 Dilemma: Structural Basis for Conformational Differences in Proinsulin B-Chain Arg22 Mutants.
Srivastav Ranganathan1, Anoop Arunagiri2
1Max Planck Institute for Physics of the Complex Systems, 01187 Dresden, Germany.
Biomolecules
|April 30, 2025
Summary
The R(B22) mutation destabilizes proinsulin, increasing childhood-onset diabetes risk. This study reveals how R(B22) normally stabilizes proinsulin structure, offering insights into protein instability and disease.
Area of Science:
- Biochemistry
- Structural Biology
- Computational Biology
Background:
- Proinsulin comprises A- and B-chains and a C-peptide.
- The B-chain is prone to diabetes-associated mutations, like R(B22)Q, causing severe loss-of-function.
- Understanding proinsulin stability is crucial for diabetes research.
Purpose of the Study:
- To investigate the role of R(B22) in proinsulin stability.
- To elucidate the molecular mechanisms underlying R(B22) mutations in diabetes.
Main Methods:
- Utilized AlphaFold-predicted structures for proinsulin.
- Employed metadynamics simulations for enhanced free energy landscape sampling.
- Analyzed effects of various R(B22) substitutions on protein stability.
Main Results:
- R(B22) stabilizes proinsulin via interaction with N86.
- R(B22) substitutions (E or Q) disrupt this interaction, increasing flexibility.
- The R(B22)Q variant favors unfolded states due to a flattened free energy landscape.
- Other substitutions also destabilize proinsulin by weakening hydrogen bonds.
- Disrupting R(B22)-N86 interaction reduces inter-chain contacts, increasing aggregation risk.
Conclusions:
- R(B22) is critical for proinsulin structural integrity.
- Proinsulin instability, driven by mutations like R(B22)Q, is linked to diabetes.
- Key inter-domain interactions are vital for protein structure and disease prevention.
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