Presenter(s): Grant Klausen
Faculty Mentor(s): Jim Prell & Jesse Wilson
Poster 43
Session: Sciences
Many therapeutic drugs target membrane proteins, many of which likely have specific lipid interactions that effect their oligomerization, structure, and function. However, only a small fraction of the proteins in the Protein Data Bank are characterized with bound lipids. Membrane protein-lipid complexes are often extremely difficult to characterize due to protein instability in solution and to the high degree heterogeneity that makes crystallization challenging.
Here, we use state-of-the-art native mass spectrometry to quantify stoichiometries and specific lipid interactions of alpha-hemolysin (AHL) toxin from Staphylococcus aureus. AHL is a well studied transmembrane toxin that shares many similarities in structure and function with other membrane toxins, such as anthrax. AHL causes host cell death by forming pores in host cell plasma membranes that lead to cell lysis. AHL is secreted as a monomer, and we have shown it oligomerizes as both a hexamer and a heptamer in detergent micelles. Our end goal is to determine if this toxin binds specifically to sphingolipids (SL) or phosphatidylcholines (PC). For this purpose, AHL is oligomerized in stable detergent micelles to which various types of lipids are titrated at specific concentrations to measure differences in binding and determine lipid specificity.. Detergents C8E4, C10E6, C12E8, DDM, OG, LDAO, and FOS-14 were tested for their ability to form AHL pores, and initial results show that both SL and PC bind strongly to the pore, but phosphatidic acid lipids do not. Results from these experiments have relevance in developing therapeutic drugs to block these interactions and neutralize the toxins.