Mutation of Schizophyllum commune metacaspase for Cleavage Site Identification

Caspases are cysteine proteases that are found in all kingdoms of life. Plants, fungi, and protozoa do not express caspase genes but instead contain homologous proteins known as metacaspases. Metacaspases possess a histidine-cysteine dyad that hydrolyses peptide bonds found after arginine and lysine residues that are recognized as cleavage locations. Many metacaspases are activated by calcium and can undergo autoproteolysis. Autoproteolysis is the self-cleavage of a protein, causing the protein to be split into smaller fragments. There are three different types of metacaspases, and our main study focuses on the five Type I metacaspases of the fungus Schizophyllum commune. It is challenging to study the metacaspase as anytime calcium is added there is a possibility that autoproteolysis can occur and only fragments of the original protein will be present. It is essential to identify potential cleavage sites in the protein to purify the intact structure. Wild-type protein has been tested to analyze the effect of increasing calcium concentration on the autoproteolysis of the metacaspase. SDS-PAGE gel results show increasing fragments as calcium concentration increases. Previous work in the lab has identified several potential lysine residues that might be cleavage sites. Metacaspase constructs have been prepared that mutate each of these lysine residues to alanine. Future work will be directed to applying similar procedures to these mutant metacaspases to verify whether cleavage locations have been eliminated by the mutations based on observing fragment changes compared to the wild-type results.