Using cross-linking probes and mass spectrometry to probe the interactions of antimicrobial peptides with lipid II.

Project ID: 2228cd1371 (You will need this ID for your application)

UCL Lead department: Chemistry

Project Summary:

The rise of antimicrobial resistance (AMR) is now a major threat to global health. Antimicrobial peptides (AMP) are currently of great interest as potential antibiotics: they frequently address novel bacterial targets with high potency and induce little antimicrobial resistance. We are currently studying nisin, a complex polycyclic AMP with five thioether-bridged rings (A – E). Nisin has nanomolar antimicrobial activity, and binds with high selectivity to to lipid II, a key biosynthetic precursor of the bacterial cell wall. A stable pore structure at a ratio of 8:4 nisin:lipid II results; however, little is known about the nisin:lipid II or nisin:nisin interactions in the pore at the molecular level. We have developed synthetic methods to make analogues of nisin (Chem-Eur J, 25, 14572 (2019)), combining solid phase peptide synthesis (SPPS) with conjugation to peptide fragments from the native peptide. In this project the student will exploit this methodology to synthesise probes to investigate the nisin:lipid II and nisin:nisin interactions in the pore, using cross-linking mass spectrometry techniques: i. The student will synthesise semi-synthetic nisin analogues incorporating photocrosslinking amino acids at specific residues in the key central ring C; ii. UV crosslinking followed by mass spectrometry will be used to determine which regions of nisin and lipid II are close to the photocrosslinker in pores in artificial membranes; iii. In parallel, zero-length crosslinkers will be used to probe the nisin:nisin and nisin:lipid II interactions at the surface of artificial membranes; iv. Docking/MD simulations will be used to generate a model for the nisin:lipid II pore. This project would suit a student with a strong background and interest in organic synthesis and chemical biology and will provide interdisciplinary training in structural mass spectrometry.