Cryo-EM structure of a mitochondrial calcium uniporter

A channel for calcium Maintaining the correct balance of calcium concentrations between the cytosol and the mitochondria is essential for cellular physiology. A calcium-selective channel called the mitochondrial calcium uniporter (MCU) mediates calcium entry into mitochondria. Yoo et al. report the high-resolution structure of MCU from Neurospora crassa. The channel is formed by four MCU protomers with differing symmetry between the soluble and membrane domains. The structure, together with mutagenesis, suggests that two acidic rings inside the channel provide the selectivity for calcium. Science , this issue p. 506