ao9b04045_si_001.pdf (1.51 MB)
Structural Characterization of the N‑Terminal Domain of the Dictyostelium discoideum Mitochondrial Calcium Uniporter
journal contribution
posted on 2020-03-21, 00:13 authored by Yuan Yuan, Chan Cao, Maorong Wen, Min Li, Ying Dong, Lijie Wu, Jian Wu, Tanxing Cui, Dianfan Li, James J. Chou, Bo OuYangThe mitochondrial calcium uniporter (MCU) plays a critical role in mitochondrial calcium uptake
into the matrix. In metazoans, the uniporter is a tightly regulated
multicomponent system, including the pore-forming subunit MCU and
several regulators (MICU1, MICU2, and Essential MCU REgulator, 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 Å 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 homologues. Biochemical and
biophysical analyses of DdMCU-NTD in solution indicated that the domain
exists as high-order oligomers. Mutagenesis showed that the acidic
residues Asp60, Glu72, and Glu74, which appeared to mediate the interface
II, as observed in the crystal structure, participated in the self-assembly
of DdMCU-NTD. Intriguingly, the oligomeric complex was disrupted 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.