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Publication Abstract from PubMed

Activation of the intracellular Ca(2+) channel ryanodine receptor (RyR) triggers a cytosolic Ca(2+) surge, while elevated cytosolic Ca(2+) inhibits the channel in a negative feedback mechanism. Cryo-EM of rabbit RyR1 embedded in nanodiscs under partially inactivating Ca(2+) conditions revealed an open and a closed-inactivated conformation. Ca(2+) binding to the high affinity site engages the central and C-terminal domains into a block, which pries the S6 four-helix bundle open. Further rotation of this block pushes S6 toward the central axis, closing (inactivating) the channel. Main characteristics of the Ca(2+)-inactivated conformation are downward conformation of the cytoplasmic assembly and tightly-knit subunit interface contributed by a fully occupied Ca(2+) activation site, two inter-subunit resolved lipids, and two salt bridges between the EF hand domain and the S2-S3 loop validated by disease-causing mutations. The structural insight illustrates the prior Ca(2+) activation prerequisite for Ca(2+) inactivation and provides for seamless transition from inactivated to closed conformations.

Ca(2+)-inactivation of the mammalian ryanodine receptor type 1 in a lipidic environment revealed by cryo-EM.,Nayak AR, Samso M Elife. 2022 Mar 8;11. pii: 75568. doi: 10.7554/eLife.75568. PMID:35257661^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.