3.A.1.5.42
Peptide transporter, SapABCDF.  The Sap transport system renders resistance against host-produced antimicrobial peptides (AMPs) amongst various Gram-negative bacteria (Dasgupta and Kanaujia 2025). The Sap system imports the AMPs across the membrane into the cytoplasm, wherein they are cleaved by proteases. The membrane components (SapBCDF) may also function as a putrescine exporter. Its multifaceted attributes in the uptake of dipeptides, AMPs, and heme were examined using molecular dynamics simulations of EcSapA in its apo and holo (bound to dipeptides, AMPs, and heme) forms. Ths was performed to gain structural insights into its molecular plasticity. The results  suggest that EcSapA possesses a wide and promiscuous binding site that is favorable for accommodating varying lengths of ligands with a ligand-dependent conformational dynamics mechanism. The estimated binding energies of the ligands suggest that EcSapA shows a preferential binding for cationic AMPs, followed by heme and dipeptides (Dasgupta and Kanaujia 2025).