Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a major class of natural products that consist of structurally diverse, therapeutically relevant molecules. All RiPPs share a common biosynthetic scheme, where a precursor peptide of ribosomal origin is modified by various biosynthetic enzymes to produce the mature RiPP product. Microviridins are one subclass of RiPPs produced by cyanobacteria that are potent serine protease inhibitors. As upregulation of serine proteases is responsible for a variety of pathologies, including lung emphysema, cystic fibrosis, and different types of cancers, designing inhibitors specific to these proteases is a key focus in medicinal research. Our work is focused on studying the biosynthesis of microviridin J, a trypsin-like protease inhibitor produced by a strain of <i>Microcystis aeruginosa</i>, and other microviridin-like products by studying the enzymes responsible for their formation. MdnA is a precursor peptide that is processed by four biosynthetic enzymes: MdnC, MdnB, MdnD, and MdnE. These enzymes are responsible for post-translational modifications on the core peptide region of MdnA that catalyze the formation of two macrolactones, one macrolactam, and one acetylation. The mature microviridin product is then transported out of the bacterial cell by an ABC transporter. So far, we have successfully utilized a disulfide crosslinking strategy between MdnC and MdnA to stabilize the co-complex that will be used for crystallization trials. Additionally, we have obtained multiple crystal hits for MdnE, homologs of MdnD, and a homolog of MdnB produced by <i>Anabaena</i> sp. PCC 7120, whose crystal structure has been partially solved to 3.51 Å. Once the biosynthesis of microviridin J is elucidated through structural characterization, we can apply protein engineering strategies to generate a library of microviridin analogs. These can be screened in a high-throughput fashion to test against disease-related proteases for eventual use in clinical studies.

Elucidating the biosynthesis of microviridins: A structural approach

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.