Journal
EMBO REPORTS
Volume 18, Issue 8, Pages 1397-1411Publisher
WILEY
DOI: 10.15252/embr.201643748
Keywords
calcium binding; cardiolipin; EF hand; mitochondria; peripheral membrane
Categories
Funding
- National Institutes of Health [DK080261, GM0077465]
- National Science Foundation
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The mitochondrial calcium uniporter is a Ca2+-activated Ca2+ channel that is essential for dynamic modulation of mitochondrial function in response to cellular Ca2+ signals. It is regulated by two paralogous EF-hand proteins-MICU1 and MICU2, but the mechanism is unknown. Here, we demonstrate that both MICU1 and MICU2 are stabilized by Ca2+. We reconstitute the MICU1-MICU2 heterodimer and demonstrate that it binds Ca2+ cooperatively with high affinity. We discover that both MICU1 and MICU2 exhibit affinity for the mitochondria-specific lipid cardiolipin. We determine the minimum Ca2+ concentration required for disinhibition of the uniporter in permeabilized cells and report a close match with the Ca2+-binding affinity of MICU1-MICU2. We conclude that cooperative, high-affinity interaction of the MICU1-MICU2 complex with Ca2+ serves as an on-off switch, leading to a tightly controlled channel, capable of responding directly to cytosolic Ca2+ signals.
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