Honors Program


Date of this Version

Spring 3-28-2022

Document Type



Warren, C. 2022. Efforts Toward Covalent Allosteric Peptide Inhibition of Caspase-6 and Frizzled-7. Undergraduate Honors Thesis. University of Nebraska-Lincoln.


Copyright Cheyenne Warren 2022


Covalent orthosteric inhibition of proteins has proven to be effective, but the potential for the inhibitor to covalently bind the incorrect protein is cause for concern1. Off-target toxicity is caused by an inhibitor molecule binding to an orthosteric site of the wrong protein. Off-target toxicity often occurs with small molecules as they are less selective, and may need only bind a portion of the substrate-binding site to prevent substrate binding. Allosteric inhibitors are one possibility to mitigate off-target toxicity. One method of allosteric inhibition that involves increased selectivity is the use of peptides as inhibitor molecules. Not only are peptides larger and thus more selective towards a specific allosteric site but they also have a unique sequence of amino acids, conferring an increased selectivity for the target protein. It is hypothesized that, through the modification of an existing protein-peptide system, the design of a covalent allosteric peptide inhibitor will yield increased affinity and selectivity when compared to other previously examined non-covalent peptides or small molecules. The two model systems chosen for this proof-of-concept study are caspase-6 with peptide pep420 and frizzled-7 with the peptide fzd7-21. The goal is to use the caspase-6 and frizzled-7 protein systems to test whether covalent allosteric peptide inhibitors improve upon other inhibitor models. Results indicate that the synthesis and dimerization of pep420 have been successful, and the pep420 dimer acts to inhibit caspase-6 activity. Future efforts will be directed toward enzymatic assays of capase-6 and frizzled-7 as well as determining the best combination of organic linker and electrophilic warhead for each model system.