Studies on Nucleophilic Cysteine Enzymes Involved in Bacterial Cell Wall Biosynthesis

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B-Lactam antibiotics are the most widely used class of antibiotics, acting through the inhibition of the bacterial cell wall synthesis. However, with increasing levels of resistance for this type of antibiotics we can no longer rely on their ability to treat common infectious diseases. L,D-transpeptidases (Ldts) are enzymes involved in bacterial cell wall synthesis that are generally not effectively inhibited by b-lactam antibiotics. The Ldts possess mostly non-essential functions, but exceptions include the M. tuberculosis LdtMt2 which is essential for virulence, and the E. faecium Ldtfm which can lead to resistance for b-lactam antibiotics. Ldts differ from other transpeptidase enzymes by employing a nucleophilic cysteine rather than a serine residue in its catalytic site. This project will involve studies on Ldts, initially focusing on LdtMt2, with a view to understanding their mechanisms and structures in detail. The project will include techniques such as MS, NMR, protein crystallography, the development of novel assays and the identification of potential Ldt inhibitors. The overall results will increase our understanding on the mechanism of cysteine enzymes and help us gain insight into the function Ldts play in bacterial survival and antibacterial resistance and may open the way to new types of inhibitors of Ldts and other classes of nucleophilic cysteine enzymes.