Description of the thesis topic

Glycans are the most structurally diverse biomolecules in nature and play pivotal roles in cellular function. They frequently undergo post-synthetic modifications, such as adding chemical groups, allowing for fine regulation of glycans function. Lysozyme is a key component of the innate immune system; it break the bacterial peptidoglycan layer and thereby contributes to the activation of the immune response. However, several Gram-positive pathogens, particularly Staphylococcus aureus, produce a membrane enzyme that acetylates peptidoglycan and inhibits lysozyme activity. The primary objective of this project is to elucidate the molecular mechanism by which enzyme acetylates peptidoglycan. During the PhD project, we aim to (1) Purify the enzyme and optimize protocol for the reconstitution of the enzyme into nanodisc or proteoliposome; (2) Employ “protein design” to stabilize target protein in different conformation; (3) Determine its three-dimensional structure using cryo-electron microscopy (cryo-EM); (4) Characterize the purified protein through biochemical, biophysical and enzymatic approaches, and (5) Develop an in vitro enzymatic assay, complemented with microbiological assay, to identify and validate inhibitors targeting this enzyme.

Work Context

The PhD student will join the emerging team “Biochemistry and Structural Biology of Membrane Proteins”, created in February 2025 at the Institute of Pharmacology and Structural Biology (IPBS) in Toulouse, an internationally recognized centre of excellence in research on infectious diseases, cancer, and inflammatory disorders. The IPBS is located on the campus of the University of Toulouse III – Paul Sabatier.
Our research thematic is multidisciplinary, aiming to characterize membrane proteins with therapeutic relevance, particularly glycan-modifying enzymes. Our core techniques are biophysics, enzymology, and structural biology (cryo-electron microscopy).