Effects of acetylation on human insulin structure, and dynamics at different temperatures: A molecular dynamics...

Insulin was used as a model protein to investigate the effects of acetylation, a significant post-translational modification. Acetylation typically targets terminal and side-chain amine groups, which, in insulin, correspond to three specific sites. Molecular dynamics simulations were conducted at pH 5.0 and three different temperatures on various acetylated insulin forms, in both monomeric and dimeric states. Two acetylation states - modification of the B-chain N-terminus alone, and modification of both the B-chain N-terminus and Lys29 - exhibited distinct properties compared with other acetylation variants. Overall, the results indicate that chemical acetylation can enhance structural compactness and reduce the propensity for protein-protein association. Key evaluated parameters included root-mean-square deviation, root-mean-square fluctuation, complex formation energy, radius of gyration, secondary structure content, and solvent-accessible surface area. At pH 5.0 and 323 K, insulin showed increased structural flexibility, accompanied by a transition from α-helix to 3₁₀-helix and β-sheet conformations, along with an increased tendency for intermolecular interactions. These findings suggest that some acetylated insulin forms may exhibit a more constrained and compact structure compared with the non-acetylated insulin form. In summary, this study provides a useful model for exploring how chemical modifications influence the secondary structure and aggregation behavior of insulin, offering valuable insights for the design of stable insulin formulations.