Sialylation of OprD hinders antibiotic entry

We have conducted molecular dynamics simulations to obtain information about the structural aspects of sialylated glycans incorporated into the OprD protein. Four N-glycosylation sites on Asn196 (NLS), Asn218 (NYT), Asn251 (NTT) and Asn288 (NGS). Out of the four sites, Asn288 site is present in the extracellular loop region having high solvent accessibility, for its proper glycosylation. Molecular dynamic studies revealed that the core glycan moiety can properly fit into Asn288 with no spatial overlap for its proper glycosylation. Simulation of sialylated-glycan in free and conjugated states depicted that the population distribution of different conformers were in good agreement with the experimental structures. The permeability of the docked antibiotic into the OprD channel revealed its binding in loop2 region and interaction with a ladder of basic amino acids helps in traversing the channel. Furthermore, we demonstrated that sialylated-glycan core structure at Asn288 blocks the channel and hinders the antibiotic binding to loop2.