Biophysical Society Conference | Tahoe 2024

Molecular Biophysics of Membranes

Poster Abstracts

8-POS Board 12 PROBING CONFORMATIONAL CHANGES OF THE MITOCHONDRIAL CALCIUM UNIPORTER USING TRANSITION METAL ION FRET Yu-Lun Huang 1 ; Ming-Feng Tsai 1 ; 1 Physiology and Biophysics, Aurora, CO, USA The mitochondrial calcium uniporter is a Ca 2+ channel that mediates Ca 2+ influx into the mitochondrial matrix. The uniporter plays a crucial role in regulating ATP synthesis, apoptosis, and intracellular calcium signaling. The uniporter contains the pore-forming MCU subunit, the auxiliary EMRE protein, and the regulatory MICU1/MICU2 subunits. It’s known that EMRE binds to MCU to open the pore, and that MICU1 gates MCU by blocking/unblocking the pore via a "ball-and-chain" mechanism. However, the mechanism by which EMRE induces conformational changes to open MCU remains unclear. Moreover, the kinetics of MICU separation from MCU is unknown. Transition metal ion FRET (tmFRET) is a powerful tool to elucidate protein conformational dynamics. I introduced a tmFRET acceptor/donor pair into the transmembrane helix 1 and coiled-coil 2 (CC2) in MCU to test the hypothesis that EMRE binding to MCU causes the movement of CC2 away the center of the pore to open the channel. I am also in the process of using stopped-flow tmFRET to determine the rate constants governing Ca 2+ -induced MICU separation from MCU. These studies represent an exciting direction to gain new insights into the molecular mechanisms underlying the uniporter’s function.

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