IP3-mediated gating mechanism of the IP3 receptor revealed by mutagenesis and X-ray crystallography

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Abstract

The inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) is an IP3-gated ion channel that releases calcium ions (Ca2+) from the endoplasmic reticulum. The IP3-binding sites in the large cytosolic domain are distant from the Ca2+ conducting pore, and the allosteric mechanism of how IP3 opens the Ca2+ channel remains elusive. Here, we identify a long-range gating mechanism uncovered by channel mutagenesis and X-ray crystallography of the large cytosolic domain of mouse type 1 IP3R in the absence and presence of IP3. Analyses of two distinct space group crystals uncovered an IP3- dependent global translocation of the curvature α-helical domain interfacing with the cytosolic and channel domains. Mutagenesis of the IP3R channel revealed an essential role of a leaflet structure in the α-helical domain. These results suggest that the curvature α-helical domain relays IP3-controlled global conformational dynamics to the channel through the leaflet, conferring long-range allosteric coupling from IP3 binding to the Ca2+ channel.

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Hamada, K., Miyatake, H., Terauchi, A., & Mikoshiba, K. (2017). IP3-mediated gating mechanism of the IP3 receptor revealed by mutagenesis and X-ray crystallography. Proceedings of the National Academy of Sciences of the United States of America, 114(18), 4661–4666. https://doi.org/10.1073/pnas.1701420114

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