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April 25, 2024 @ 13:30 - 14:30
CRBI Seminar – Dr. Martin Schmeing, McGill University Thursday April 25th 2024
Biosynthesis and use of the most interesting polymer you didn’t know existed
Abstract:
Cyanophycin is a natural product polymer with a poly-aspartate backbone and arginines linked to each Asp side chain. Used in bacteria for storage of fixed nitrogen, carbon and energy, long chains of cyanophycin coalesce into inert, membrane-less granules which can occupy most of the volume of a cell. Cyanophycin has a variety of potential green industrial and biomedical applications. Cyanophycin is made by cyanophycin synthetase 1 or 2 through ATP-dependent polymerization of Asp and Arg, or β-Asp-Arg, respectively. It is degraded into dipeptides by specialized exo-cyanophycinases, and these dipeptidase are hydrolyzed into free amino acids by nonspecific isoaspartyl dipeptidases. I will share highlights of our structural and functional studies of cyanophycin biosynthesis and degradation, which led to surprising discoveries: Our structures and biochemical assays of the cyanophycin synthetase 1 revealed it to be a remarkable, multi-domain, multi-functional biosynthetic machine and uncovered a hidden hydrolytic active site that is crucial for rapid biosynthesis. We also showed that cyanophycin synthetase 2 can assume several elegant architectures that influence its synthetic activity. Further, we discovered and characterized a novel, large family of isoaspartyl dipeptidases dedicated to cyanophycin metabolism, which allows the human pathogen Pseudomonas aeruginosa to use β-Asp-Arg as a sole carbon source, and as good a sole nitrogen source as ammonium. Bioinformatics results underscore how common it is for bacteria to be cyanophycin producers or scavengers, much more so than currently appreciated.