Role of surface-exposed charged basic amino acids (Lys, Arg) and guanidination in insulin on the interaction and stability of insulin-insulin receptor complex

Naturally occurring proteins are emerging as novel therapeutics in the protein-based biopharmaceutical industry for the treatment of diabetes and obesity. However, proteins are not suitable for oral delivery due to short halflife, reduced physical and chemical stability and low permeability across the membrane. Chemical modification has been identified as a formulation strategy to enhance the stability and bioavailability of protein drugs. The present study aims to study the effect of charge-specific modification of basic amino acids (Lys, Arg) and guanidination on the interaction of insulin with its receptor using molecular modelling. Our investigation revealed that the guanidination of insulin (Lys-NHC = NHNH2) enhanced and exerted stronger binding of the protein to its receptor through electrostatic interaction than native insulin (Lys-NH3+). Point mutations of Lys and Arg (R22, K29; R22K, K29; R22, K29R; R22K, K29R) were attempted and the effects on the interaction and stability between insulin/modified insulins and insulin receptor were also analyzed in this study. The findings from the study are expected to provide a better understanding of the possible mechanism of action of the modified protein at a molecular level before advancing to real experiments.

Automated summary

This study investigates the impact of charge-specific modification on the interaction between insulin and its receptor, using molecular modelling to analyze the effects on protein stability and bioavailability. Results show that guanidination of insulin enhances the binding to its receptor through electrostatic interactions, providing insights for potential mechanisms of action at a molecular level before moving on to real experiments.