Formation of Protamine and Zn–Insulin Assembly: Exploring Biophysical Consequences

• DOI: 10.1021/acsomega.2c04419
• Publication Date: 2022-11-04T07:53:33Z
• Authors: Soumya Aggarwal; Neetu Tanwar; Ankit Singh; Manoj Munde
• Keywords: Isothermal Titration Calorimetry

The insulin-protamine interaction is at the core of mode action in many insulin formulations (Zn + protamine) and to treat diabetes, which protamine added stable form hexameric (Zn-insulin). However, due unavailability quantitative data a high-resolution structure, binding mechanism complex remains unknown. In this study, it was observed that Zn-insulin experiences destabilization as by loss secondary structure circular dichroism (CD), reduction thermal stability melting upon binding. isothermal titration calorimetry (ITC), found interactions were mostly enthalpically driven. This line with positive ΔCm value (+880 cal mol-1), indicating role hydrophilic formation, exposure hydrophobic residues solvent, firmly supported 8-anilino-1-naphthalene sulfonate (ANS) study. stoichiometry (N) ITC suggests multiple molecules chain, consistent picture condensation presence protamine. Atomic force microscopy (AFM) suggested formation heterogeneous Zn-insulin-protamine complex. fluorescence, strong Tyr quenching, suggesting location protamine-binding site near Tyr, also molecular docking Since critical stabilization self-assembly, its may impair insulin's self-association ability thermodynamic while same time promoting flexible conformation desired for better biological activity.