Eating the poison: characterisation of the molecular basis of antimicrobial peptide resistance in pathogenic Escherichia coli (360G-Wellcome-105501_Z_14_Z)

Cationic antimicrobial peptides (CAMPs) are produced by the human immune system as a defence mechanism against invading bacteria. However, bacteria have evolved resistance to CAMPs by transporting them into the cell for degradation, preventing them from disrupting the bacterial membrane and therefore promoting infection. This project aims to characterise the ability of the Sap system transporter protein, SapA, to bind and transport a range of CAMPs. The project will incorporate aspects of structural biology, computational modelling and genetic and microbiological work. This interdisciplinary integrated approach will enable an accurate understanding of the Sap system. Structural studies of SapA via x-ray crystallography will allow analysis of how SapA is able to bind long CAMPs, which is unusual amongst ABC transporters. Docking and modelling of the solved structures with a compound fragment library will enable the design of potentially tighter binders than CAMPs, identifying possible new drugs to bypass the resistance mechanism. Moving into the functional studies, susceptibility tests with genetically modified bacterial strains to express increased/decreased levels of peptidases will identify whether CAMPs are broken down by peptidases once transported into the cell. This will help identify the mode of CAMP resistance in bacteria and possibly another drug target.