Garneau-Tsodikova Lab
Research
Mechanistic Studies of Enzymes Involved in Nonribosomal Peptide Biosynthesis | Combinatorial Biosynthesis
Mechanistic Studies of Enzymes Involved in Nonribosomal Peptide Biosynthesis
With the worldwide emergence of resistance to currently available antibiotics and anticancer agents, there is an increasing demand for new clinically useful drugs. Over the past ten years, tremendous efforts have been made to exploit marine and terrestrial microorganisms for drug discovery. A large number of linear and cyclic nonribosomal peptides have been found to be therapeutic agents. These compounds are biosynthesized by large, multimodular enzymes, the nonribosomal peptide synthetases (NRPSs), organized into discrete modules. Each module contains three core domains (condensation (C), adenylation (A), and thiolation (T)) and is responsible for the incorporation of one amino acid into the growing peptide chain. Additional diversity is introduced into the peptide chain by auxiliary domains: epimerization (E), methylation (MT), oxidoreductase (Ox), reductase (R), and cyclization (Cy). There is a tremendous interest in modifying the structure of nonribosomal peptides to increase their biological activity. However, these compounds are often quite large and difficult to access by traditional synthetic methods. We aim to design and biosynthesize "unnatural" biologically active nonribosomal peptides by genetic and biochemical manipulations. To achieve this goal a thorough understanding of the mechanisms by which Nature assembles and introduces such diversity into these bioactive molecules is required. We are currently performing mechanistic studies on a variety of interesting bond formations and ring closures.
We are currently focusing on studying the individual steps of the biosynthesis of the anticancer agent thiocoraline. Thiocoraline belongs to the family of bisintercalator natural products that bind duplex DNA through their two planar intercalating chromophores.
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Combinatorial Biosynthesis
Combinatorial chemistry has revolutionized the world of organic chemistry. It is an extremely powerful technique that allows for the design and chemical synthesis of large libraries of small organic molecules rapidly. In contrary to traditional synthesis where compound A would react with compound B to generate a unique compound AB, the principle of combinatorial chemistry consists of mixing a range of building blocks C with a variety of building blocks D to generate a library of many hundreds or thousands of compounds CD. Combinatorial chemistry has been widely used by chemists for the past decade to design and discover new drugs. In our group, we apply the general principles of combinatorial chemistry to develop tools, strategies, and support for potential use in combinatorial biosynthesis, a field still in its infancy. With the ultimate goal of generating novel nonribosomal peptides by combinatorial biosynthesis, we currently focus on understanding the structural requirements for communication between different domains of the nonribosomal peptide synthetase (NRPS) assembly line. We are also working on engineering novel NRPS assembly lines to be used in a combinatorial fashion.
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