Tackling Antibiotic Resistance With Covalent Macrocycles

Infections with multidrug-resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA) are major threats to human health. Discovering novel druggable targets for antibiotic development is a pivotal task to guarantee effective treatment in the future. Lipoteichoic acid synthase (LtaS) catalyses the synthesis of

lipoteichoic acid (LTA) from phosphatidylglycerol and is a key enzyme for S. aureus cell wall biosynthesis. LtaS is an attractive antimicrobial target as Gram-positive bacteria that lack LTA exhibit impaired cell division and growth defects. In this PhD project, you will use a phage display approach, developed in the Lovell lab, to identify a potent and

selective covalent cyclic peptide (CCP) antagonist for LtaS. You will screen in-house compound libraries to identify covalent fragments that modify Lys299 in the active site of LtaS (Fig. 1A). Hit fragments will be resynthesized as linchpin derivatives and grafted onto peptide phage display libraries to generate billions of

Lys299- directed CCPs to screen against LtaS (Fig. 1B). You will carry out multiple rounds of phage panning and amplification and perform bioinformatic analyses to prioritize enriched CCPs for synthesis and testing in surface plasmon resonance binding studies. Working with the Spencer lab you will obtain co-crystal structures of hit

CCPs bound to LtaS revealing critical interacting residues and enabling structure-guided optimization of key molecule parameters such as selectivity and proteolytic stability. You will validate the proteome-wide selectivity of CCPs using chemical proteomics approaches. Working with the Laabei and van den Elsen labs you will apply

the lead CCP to a panel of MRSA isolates and assess changes in LTA biosynthesis and growth rate. Finally, you will assess the effects of inhibiting LtaS in vivo by incubating the lead CCP with Manduca Sexta Larvae challenged with S.aureus. Your PhD research will validate LtaS as an actionable therapeutic target for the treatment of MRSA infections

and will provide an optimized molecule for further pre-clinical assessment.