High-resolution structure of a partially folded insulin aggregation intermediate.

Area of Science:

• Biochemistry
• Structural Biology
• Protein Science

Background:

• Insulin aggregation is crucial in manufacturing and extensively studied structurally.
• The molecular triggers for insulin aggregation remain unclear.
• Understanding insulin aggregation is vital for developing stable therapeutic proteins.

Purpose of the Study:

• To elucidate the molecular mechanisms initiating insulin aggregation at acidic pH.
• To characterize the structural features of the aggregation-prone intermediate.
• To inform the engineering of aggregation-resistant insulin variants.

Main Methods:

• High-resolution structural analysis of insulin intermediates.
• Biophysical characterization of protein folding and aggregation.
• Comparative structural analysis of monomeric and intermediate states.

Main Results:

• At acidic pH, insulin aggregation is initiated by a partially folded monomeric intermediate.
• This intermediate exhibits disordered A-chain helices and a displaced B-chain helix compared to the stable monomer.
• A central hydrophobic cavity is formed in the intermediate, serving as a potential nucleation site for oligomerization.

Conclusions:

• The partially folded monomeric intermediate is a key species in insulin aggregation at acidic pH.
• Structural insights into this intermediate can guide the development of more stable insulin formulations.
• Targeting this transition may lead to insulin variants with improved pharmacokinetic properties and aggregation resistance.