Dr. Anthony J.Clarke

Dr. Anthony J.Clarke |Clyto Access

Professor, University of Guelph, Canada

Organizing Committee Member

Expertise: Biochemistry, Molecular Biology, Genetics

Biography:


Dr. Anthony J.Clarke obtained his Ph.D from the University of Waterloo in Chemistry in 1983. He joined the University of Guelph in 1986 as an assistant professor after post-doctoral stints at the Carlsberg Research Centre, Copenhagen and the National Research Council, Ottawa. Soon after establishing himself in the academic ranks, he was drawn into the University’s administration and he has served as departmental chair, college dean, Associate V.P. (Research), and Dean of Graduate Studies, and Assistant V.P. (Graduate Studies and Program Quality Assurance).Presently he is working as a professor at University of Guelph, Canada.

Presentation:

Title: Peptidoglycan O-acetyltransferase A (OatA) as an anti-virulence target in Gram-positive pathogens: its structure, mechanism of action, and inhibition.

Abstract:

Many important Gram-positive pathogens, such as Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae evade host innate immune defenses by modifying their peptidoglycan (PG) sacculus through O-acetylation. The O-acetylation of PG occurs at the C6-OH of N-acetylmuramoyl residues and the enzyme responsible has been identified as O-acetyltransferase A (OatA), a predicted bi-domain membrane protein composed of a putative transmembrane domain and a C-terminal globular catalytic domain. In this presentation, the biochemical characterization and X-ray crystal structure of the C-terminal catalytic domain of OatA (OatAC) from S. pneumoniae and S. aureus are described. The Michaelis-Menten parameters for various surrogate acetyl-donors and acetyl-acceptors were determined for OatAC using a chromogenic assay coupled with mass spectrometric analysis. A novel homopolymeric PG-based substrate was used to delineate the unique specificities for the two enzymes which account for their different temporal activities in PG metabolism. The structure of OatAC adopts an atypical α/β hydrolase fold comparable to SGNH esterases. However, a different oxyanion loop-orientation in the active site of OatAC compared to the SGNH esterases was found. To probe the effect of this change on the mechanism, the structure of OatAC was determined in complex with methanesulfonate covalently bound to the catalytic serine. This structure mimics the tetrahedral transition state for the attack of water on acetyl-enzyme intermediates and shows that a conformational change occurs in the active site thereby minimizing the access of water. Finally, a high-throughput screen was conducted to identify inhibitors of the S. aureus enzyme which will facilitate the development of leads to a new class of antibacterial/antivirulence drugs.

Related Conferences :

International Biotechnology and Pharmaceutical Industry Forum