Two-state conformational changes in inositol 1,4,5-trisphosphate receptor regulated by calcium

Kozo Hamada*, Tomoko Miyata, Kouta Mayanagi, Junji Hirota, Katsuhiko Mikoshiba

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

79 Citations (Scopus)


Inositol 1,4,5-trisphosphate receptor (IP3R) is a highly controlled calcium (Ca2+) channel gated by inositol 1,4,5-trisphosphate (IP3). Multiple regulators modulate IP3-triggered pore opening by binding to discrete allosteric sites within IP3R. Accordingly we have postulated that these regulators structurally control ligand gating behavior; however, no structural evidence has been available. Here we show that Ca2+, the most pivotal regulator, induced marked structural changes in the tetrameric IP3R purified from mouse cerebella. Electron microscopy of the IP3R particles revealed two distinct structures with 4-fold symmetry: a windmill structure and a square structure. Ca2+ reversibly promoted a transition from the square to the windmill with relocations of four peripheral IP3-binding domains, assigned by binding to heparin-gold. Ca2+-dependent susceptibilities to limited digestion strongly support the notion that these alterations exist. Thus, Ca2+ appeared to regulate IP3 gating activity through the rearrangement of functional domains.

Original languageEnglish
Pages (from-to)21115-21118
Number of pages4
JournalJournal of Biological Chemistry
Issue number24
Publication statusPublished - 14 Jun 2002
Externally publishedYes


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