Theoretical Study of the Influence of K20N Glycosylation on the Dynamic Behavior of Im7 Protein

This study employed molecular dynamics simulations to investigate the impact of N-linked glycosylation (GlcNAc₂) at the K20N position on the structural dynamics and stability of the bacterial immunity protein Im7. Simulations were conducted in both aqueous and 2 M urea denaturing environments. The simulation results in aqueous solution indicate that glycosylation has only a minor effect on the protein, consistent with expectations. In contrast, simulations in urea reveal that K20N glycosylation significantly destabilizes Im7. Analyses of RMSD, native contacts, SASA, RMSF, correlation matrix, PCA, helical content and hydrophobic centroid distance consistently demonstrate that K20N glycosylation increases the flexibility of Helix I and Helix II and weakens the concerted motion among helical domains (particularly between Helix I and Helix II/IV). The destabilizing effect of K20N glycosylation on Im7 originates in Helix I (where glycan attaches) and propagates to Helix II and the loop region connecting Helix I and Helix II. The instability of Helix II is closely associated with the disruption of hydrophobic interactions within the hydrophobic core. These findings provide new insights into the relationship between site-specific glycosylation and protein stability.