S. aureus Peptidoglycan recognition by SH3b domains

• Autor(a) principal: Seco, Francisco
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/161277
• topic: MRSA; Peptidoglycan; Endolysins; Cell binding domains; SH3b; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Antimicrobial resistance is one of biggest health problems worldwide. Every year it is responsible for thousands of deaths and large hospital costs and the World Health Organization (WHO) expects this problem will increase in the future. One of the microorganisms responsible for this phenomenon is methicillin-resistant Staphylococcus aureus. Endolysins have emerged as one of the most promising combat options against this multidrug resistant strains. Endolysins are enzymes encoded by bacteriophages that hydrolyze the cell wall of target bacteria, with minimal risk for resistance acquisition. The purpose of this work is to characterize the recognition of S. aureus peptidoglycan by two distinct cell binding domains (CBD). These domains come from the endolysin Twort and MW2 S. aureus strain and despite not having sequence homology, both have a SH3b-type structure. To this end, various Nuclear Magnetic Resonance (NMR) methods were used to characterize different peptidoglycan fragments and monitor their interaction with the 2 CBDs, from both the peptidoglycan and the binding domains point of view. The results show that neither domain interacts with the sugar component and, for both, the D-iso-Glutamine residue of the tetrapeptide is important for binding. This suggests that there is only one binding site in CBDMW2 that interacts with a restricted region of the tetrapeptide, while CBDTwort has 2 opposite sites that interact with different peptidoglycan components. However, the inefficiency of peptidoglycan isotopic labeling proved to be a limiting factor in this analysis, and it is necessary to develop a new labeling protocol which allows a more complete characterization.