Structure Changes of Ion-motive ATPases

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DESCRIPTION (provided by applicant): The proposed research focuses on the SERCA calcium pump and the NKA sodium pump. These are two of a class of proteins called "Ion-motive ATPases", enzymes that use the energy of ATP to pump ions across cell membranes. Ion pumps play an important role in all cells, and disordered function of these enzymes is associated with human disease, including heart failure. The proposed research will use advanced fluorescence methods to measure the structures and motions of ion pumps in living cardiac muscle cells. We will test three major hypotheses: 1) Ion pumps undergo very large structure changes. 2) These large slow changes are regulated by fast protein dynamics. 3) Regulatory partners continually bind and unbind from the pump with fast kinetics. By measuring ATPase structures and motions in live cardiac cells, we will gain new insight into mechanisms that become disrupted in failing cardiac muscle. PUBLIC HEALTH RELEVANCE: Ion pumps occupy a central position in human health, and they are key targets for therapeutic intervention in several important disease processes including heart failure. This research focuses on two ion pumps: the sodium pump (NKA) and the calcium pump (SERCA). Disordered NKA function is associated with hypertrophy and heart failure. Targeting this pump with inhibitory drugs is one of the oldest and most effective treatments for the inadequate contractility of the failing heart. SERCA is responsible for pumping calcium, the ion that coordinates the contraction and relaxation of the cardiac muscle. Optimal calcium handling is critical for normal cardiac function, and deranged SERCA activity has been implicated as a cause and an effect of heart failure. A comparison of these structurally similar pumps will yield insight into common functional mechanisms, and may reveal new opportunities to intervene in the process of heart disease.