BMBDG Seminar: Ph.D. Exit Seminar – John Chen
Title: Mutational scanning of metallo-β-lactamases to probe functional determinants, selection pressure dependence and homolog incompatibilities
Abstract: Enzymes known as metallo-β-lactamases (MBLs) are a major source of bacterial resistance against β-lactams, one of the most widely used classes of clinical antibiotics. MBLs degrade almost all classes of β-lactams with high efficacy, and can be transmitted on plasmids. Detailed understanding of MBLs in terms of their sequence-function relationships can be beneficial in the design of new antibiotics or inhibitors, understanding how mutations affect MBL function can help understand and predict their evolution, and give general knowledge on how mutations could be leveraged in protein engineering. Although there are numerous detailed studies of MBLs, our knowledge is limited to a handful of residues in a small number of sequences. A recently developed method known as deep mutational scanning (DMS) can enable us to construct comprehensive sequence-function maps of proteins. Using DMS, we comprehensively explored the sequence-function relationship of 2 representative MBL homologs, NDM-1 and VIM-2. The DMS data revealed the key functional requirements of the MBLs, including those on activity, stability and substrate specificity. Furthermore, DMS conducted across different antibiotic concentrations allows us to explore the concentration dependence of sequence-function relationships. Finally, comparisons between NDM-1 and VIM-2 datasets revealed prevalent epistasis, with further analysis highlighting the structural trends and interactions that underlie such observations.
Monday, July 18, 2022 at 2:30 pm – 3:30 pm via Zoom
Hosted by: Dr. Nobuhiko Tokuriki
BMBDG Seminar: Ph.D. Exit Seminar – Bronwyn Lyons
Posted on March 31, 2022
Title: Structural investigation of the Enteropathogenic Escherichia coli type 3 secretion system.
Abstract: “Enteropathogenic Escherichia coli (EPEC) is frequently a cause of diarrheal disease, stemming from produce contamination due to farm waste run-offs, and inadequate supply of clean water. Virulence mechanisms that these bacteria employ to cause disease are conserved across many pathogens, such as those responsible for sexually transmitted infections (e.g. chlamydia) or food poisoning (e.g. salmonellosis). The type 3 secretion system (T3SS) is a syringe-like proteinaceous channel that spans the inner and outer membranes of the bacterial cell, projecting into the extracellular medium where it interacts with the host cell membrane to deliver virulence factors. As with many virulence mechanisms, the T3SS is not required for the survival of these bacteria and therefore are promising targets for the development of anti-virulence compounds that can potentially block their propensity to cause disease. The overall goal of this thesis has been to study the T3SS of EPEC by employing a toolbox of structural biology methods. Components of the system in EPEC are studied using various cryo-electron microscopy techniques and nuclear magnetic spectroscopy. Structural characterization of T3SS components allows for inference of function and exploration of these hypotheses using in vivo methods. This work furthers our comprehension about the structure, and by extension function, of the components that comprise the Gram-negative T3SS virulence machinery in EPEC and lays the foundation for development of anti-virulence therapeutics targeting a variety of pathogenic bacteria. ”
Monday, July 04, 2022 at 2:30 pm – 3:30 pm via Zoom
Hosted by: Dr. Natalie Strynadka
