Evolutionary Optimization of Cyclic Peptides for Protease Inhibition

One of the most abundant tasks of biopharmaceuticals is the binding and blocking of deregulated proteins. Towards this goal we mutate and select microviridins, which are tricyclic depsipeptides from cyanobacteria. They are small but stable due to their post-translational side-chain crosslinking and have high therapeutic potential for e.g. blocking proteases linked to diseases. Yet the possibilities of cyclic peptides are largely untapped since genetic systems for evolutionary optimization are not existent or not well established. Thus, we are developing systems for the production, mutation, and selection of such peptides. For production, we use the 6.5 kilo base mdn gene cluster cloned in E. coli plasmids. For mutation, we apply error prone PCR in combination with efficient cloning. For selection, we are establishing and testing phage display as well as an in-vivo selection device, which links blocking of protease activity to antibiotic resistance. The research presented was conducted by a student team in the context of the iGEM competition.