Abstract Title

The Investigation of the Suicidal Phenotypes of K1 “Killer Toxin” Truncations in Saccharomyces cerevisiae

Additional Funding Sources

The project described was supported by a student grant from the UI Office of Undergraduate Research.

Abstract

Common antifungal treatments such as fluconazole or miconazole are becoming less effective in treating fungal infections. The diminishing efficiency of such treatments is due to fungal pathogens developing an increased resistance to antimycotic drugs. Therefore, the use of antifungal “killer toxins” has become a recent focus of research in understanding how to combat these fungal infections in place of current antimycotics. This project examined the lethal effects of the K1 toxin to provide a better understanding of the K1 mechanism of action against fungi. K1 is a heterodimeric protein which consists of two different polypeptide chains: “alpha” (α) and “beta” (Β) which are linked by a single disulfide bond. It has been previously reported that the isolated α-domain of the K1 toxin (K1-α) is able to cause cell death when ectopically expressed by yeast cells. We have confirmed this phenotype by first cloning and then expressing the isolated K1-α domain in Saccharomyces cerevisiae using a galactose-inducible expression plasmid. This caused lethality when cells were grown on galactose media which induced the expression of K1-α. To understand the host proteins that are important for K1-α lethality, the systematic gene deletion collection library of non-essential genes in S. cerevisiae is now being screened for suppressor mutants. We have identified clones that appear to be resistant to K1-α expression and are in the process of identifying the gene deletions. This will lead us to a better understanding of the mechanism of action of the K1-α toxin and why it is cytotoxic to yeasts.

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The Investigation of the Suicidal Phenotypes of K1 “Killer Toxin” Truncations in Saccharomyces cerevisiae

Common antifungal treatments such as fluconazole or miconazole are becoming less effective in treating fungal infections. The diminishing efficiency of such treatments is due to fungal pathogens developing an increased resistance to antimycotic drugs. Therefore, the use of antifungal “killer toxins” has become a recent focus of research in understanding how to combat these fungal infections in place of current antimycotics. This project examined the lethal effects of the K1 toxin to provide a better understanding of the K1 mechanism of action against fungi. K1 is a heterodimeric protein which consists of two different polypeptide chains: “alpha” (α) and “beta” (Β) which are linked by a single disulfide bond. It has been previously reported that the isolated α-domain of the K1 toxin (K1-α) is able to cause cell death when ectopically expressed by yeast cells. We have confirmed this phenotype by first cloning and then expressing the isolated K1-α domain in Saccharomyces cerevisiae using a galactose-inducible expression plasmid. This caused lethality when cells were grown on galactose media which induced the expression of K1-α. To understand the host proteins that are important for K1-α lethality, the systematic gene deletion collection library of non-essential genes in S. cerevisiae is now being screened for suppressor mutants. We have identified clones that appear to be resistant to K1-α expression and are in the process of identifying the gene deletions. This will lead us to a better understanding of the mechanism of action of the K1-α toxin and why it is cytotoxic to yeasts.