Training Group:

Membrane Biology

Mentor / Lab:

Christine Hrycyna

Specific Research Area / Project:

Mapping of the Ste24 Binding Site

Lab / Personal work-related websites:

Lab Website

Research Profile:

Human zinc metalloprotease (ZMPSTE24) is an intracellular transmembrane protein which performs two cleavages on the peptide substrate, prelamin A. The first cleavage functions as a proteolytic step in the CaaX processing pathway, removing the three C-terminal (-aaX) residues. Following CaaX modifications, ZMPSTE24 removes the newly modified C-terminal tail. While the function of ZMPSTE24 has been most well-defined in prelamin A maturation, earlier this year it was found that ZMPSTE24 may also prevent the aggregation of the amyloid-forming protein, IAPP, found in type II diabetes. The mechanism of this second function of ZMPSTE24 still remains unclear.

The crystal structures for both ZMPSTE24 and the yeast homolog, Ste24, have been solved, revealing a novel protein shape. Both proteins contain seven transmembrane helices which surround a large, water-filled chamber of mixed hydrophobicity which is capped on both sides by additional helices. The active site lies within the chamber, meaning the substrate must enter the chamber and be recognized at two different sequences for proteolysis.

Insight into how the protease recognizes and binds the peptide substrate is unknown.

The goal of this project is to characterize residues of Ste24 by their role in substrate binding. To achieve the goal, mutant forms of Ste24 are created and characterized by their residual activity with respect to wildtype. A photoactivatable analog of the well-defined Ste24 substrate is then used to observe possible changes in substrate affinity. In addition, tandem MS/MS and microscale thermophoresis methods are currently being developed to obtain more specific information in response to the location of substrate binding.

About Me:

All through my undergrad career I knew I wanted to get my PhD. At the time I really wanted to do research in infectious diseases. When it came down to it though, I liked the idea of the Purdue Life Sciences interdisciplinary program (PULSe) to be a great option for me because it allowed me to try several different areas of research. That was what helped me make my final decision to attend Purdue for graduate school, and while I don’t currently work with infectious diseases, I think the research I am doing is quite rewarding.

Awards:

• Outstanding Biochemistry Graduate, Lake Superior State University, 2015
• Margaret Haag Memorial Endowed Scholarship, Lake Superior State University, 2014-2015

Publications:

• Ellsworth, A., Magyar, C., Hubbell, G., Theisen, C., Holmes, D., Mosey, R. “One-pot triflic anhydride-mediated synthesis of 1,2-disubstituted 2-imidazolines from N-(2-haloethyl)amides and amines.” Tetrahedron 2016, pg. 6380-6389.
• Ratnayake, N., Theisen, C., Walter, T., Walker, K. “Whole-cell biocatalytic production of variously substituted ß-aryl- and ß-heteroaryl-ß-amino acids.” Journal of Biothenology 2016, pg. 12-21.

Presentations:

• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C.A. (January 2019) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site” Oral presentation at the PULSE Welcome Session week 2, West Lafayette, IN.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C.A. (January 2019) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site” Oral presentation at the PULSe Welcome Session Week 1 5 minute Thesis competition, West Lafayette, IN.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C.A. (May 2018) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site” Oral presentation at the Hitchhiker's Guide to the Biomolecular Galaxy symposium, West Lafayette, IN.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C.A. (February 2018) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site”Poster presentation at the Health and Disease poster session, West Lafayette, IN.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C.A. (July 2017) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site”. Poster presentation at the FASEB Research Conference, Saxton River, VT.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C. A. (May 2017) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site”. Poster presentation at the Hithhiker’s Guide to the Biomolecular Galaxy Conference, West Lafayette, IN.
• Theisen, C., Hsu, E., Wiley, P., Vervacke, J., Distefano, M., Hrycyna, C. A. (April 2017) “Mutational Analysis and Characterization of the Ste24p Substrate Binding Site”. Poster presentation at the Office of Interdisciplinary Graduate Programs Conference, West Lafayette, IN.
• Theisen, C., Heintz, V., Wang, L., LaCount, D. “Preparing Marburg Virus Protein Fragments for Future Host-Pathogen Interactome Studies.” Poster presentation at PULSe Spring Reception, West Lafayette, IN.
• Theisen, C., Mosey, R. A. (April 2015) “Synthesis of N-(2-haloethyl)amides and 1,2-Disubstituted 2-Imidazolines”. Poster and oral at Lake Superior State University Senior Thesis Symposium, Sault Ste. Marie, MI.
• Theisen, C., Ratanayake, R. M. D., Walker, K. D. (July 2013) “Use of Bacteria Engineered with an Aminomutase to Produce Non-Natural ß-Amino Acids In-Vivo.” Poster and oral presentation at MidSURE Poster Symposium and Plant Genomics at MSU Research Symposium, East Lansing, MI.

Leadership:

• United Way Event Planner Volunteer, 2019
• Hitchhiker’s Guide to the Biomolecular Galaxy Symposium Organizer, 2018-2019
• Purdue University Life Sciences Program Mentor, 2016-2017