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bioRxiv · 10.1101/848002

Structural characterization of the N-terminal domain of the Dictyostelium discoideum mitochondrial calcium uniporter

Yuan, Y.·Cao, C.·Wen, M.·Li, M.·Dong, Y.·Wu, L.·Wu, J.·Cui, T.·Li, D.·Chou, J. J.·OuYang, B.
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Abstract

The mitochondrial calcium uniporter (MCU) plays a critical role in the mitochondrial calcium uptake into the matrix. In metazoans, the uniporter is a tightly regulated multi-component system including the pore-forming subunit MCU and several regulators (MICU1, MICU2, EMRE). The calcium-conducting activity of metazoan MCU requires the single-transmembrane protein EMRE. Dictyostelium discoideum (Dd), however, developed a simplified uniporter for which the pore-forming MCU (DdMCU) alone is necessary and sufficient for calcium influx. Here, we report a crystal structure of the N-terminal domain (NTD) of DdMCU at 1.7 [A] resolution. The DdMCU-NTD contains four helices and two strands arranged in a fold that is completely different from the known structures of other MCU-NTD homologs. Biochemical and biophysical analyses of DdMCU-NTD in solution indicated that the domain exists as oligomers, most probably as a pentamer or hexamer. Mutagenesis showed that the acidic residues Asp60, Glu72 and Glu74, which appeared to mediate the parallel interface as observed in the crystal structure, participated in the self-assembly of DdMCU-NTD. Intriguingly, the oligomeric complex readily dissociated to lower-order oligomers in the presence of calcium. We propose that the calcium-triggered dissociation of NTD regulates the channel activity of DdMCU by a yet unknown mechanism.

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Yuan, Y., Cao, C., Wen, M., Li, M., Dong, Y., Wu, L., Wu, J., Cui, T., Li, D., Chou, J. J., OuYang, B.. 2019-11-20. Structural characterization of the N-terminal domain of the Dictyostelium discoideum mitochondrial calcium uniporter. https://doi.org/10.1101/848002

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