Understanding the structures and interactions of proteins that interact with membranes has many implications. Membrane proteins play roles in the transfer of necessary materials and information between cells and their environments as well as within cells (e.g., between the cytosol and organelles). As such, they currently constitute more than half of all drug targets, and some peptides, such as antimicrobial peptides (AMPs), are also being investigated for their therapeutic use in treating bacterial infections for humans. However, studying the structures of membrane proteins has proven more challenging compared to soluble proteins. This is due to the necessity of including the membrane or a good membrane mimic to ensure the integrity of the membrane protein remains intact, as poor mimics or no membrane can detrimentally affect membrane protein structure and function. Some proteins, like the AMP chionodracine, are highly amenable to study with methods such as solution NMR spectroscopy (Chapter 2), but larger membrane proteins prove challenging or impossible to measure in solution due to the molecular weight limitations and frequently do not crystallize easily either. Solid-state NMR spectroscopy (ssNMR) has helped to overcome these obstacles and more methodology continues to be developed expanding the application of ssNMR. For example, Chapters 3 and 4 of this thesis describe new ssNMR methods using the sarco(endo)plasmic reticulum (SERCA) and sarcolipin (SLN), respectively. SERCA and SLN form a crucial complex in the membrane of the sarcoplasmic reticulum in skeletal muscles cells. Muscle relaxation is largely controlled by SERCA pumping calcium out of the cytosol using energy from ATP hydrolysis, and SLN inhibits SERCA as well as uncouples the ATP hydrolysis and calcium transport. SLN’s effect on SERCA leads to more heat production, which may be important to thermogenesis in mammals as well as an additional mechanism to control energy expenditure. Chapter 5 primarily uses ssNMR with the goal to better understand the mechanism by which SLN inhibits and uncouples SERCA. Overall, gaining a better understanding of how SERCA is regulated will aid in developing therapies for diseases resulting from improper calcium cycling.
University of Minnesota Ph.D. dissertation. May 2017. Major: Biochemistry, Molecular Bio, and Biophysics. Advisor: Gianluigi Veglia. 1 computer file (PDF); x, 183 pages.
Biophysical Characterization of Interactions Between Two Membrane Proteins: SERCA and Sarcolipin.
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