An apical Phe-His pair defines the Orai1-coupling site and its occlusion within STIM1

Yandong Zhou, Michelle R. Jennette, Guolin Ma, Sarah A. Kazzaz, James H. Baraniak, Robert M. Nwokonko, Mallary L. Groff, Marcela Velasquez-Reynel, Yun Huang, Youjun Wang, Donald L. Gill

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Ca2+ signal-generation through inter-membrane junctional coupling between endoplasmic reticulum (ER) STIM proteins and plasma membrane (PM) Orai channels, remains a vital but undefined mechanism. We identify two unusual overlapping Phe-His aromatic pairs within the STIM1 apical helix, one of which (F394-H398) mediates important control over Orai1-STIM1 coupling. In resting STIM1, this locus is deeply clamped within the folded STIM1-CC1 helices, likely near to the ER surface. The clamped environment in holo-STIM1 is critical—positive charge replacing Phe-394 constitutively unclamps STIM1, mimicking store-depletion, negative charge irreversibly locks the clamped-state. In store-activated, unclamped STIM1, Phe-394 mediates binding to the Orai1 channel, but His-398 is indispensable for transducing STIM1-binding into Orai1 channel-gating, and is spatially aligned with Phe-394 in the exposed Sα2 helical apex. Thus, the Phe-His locus traverses between ER and PM surfaces and is decisive in the two critical STIM1 functions—unclamping to activate STIM1, and conformational-coupling to gate the Orai1 channel.

Original languageEnglish (US)
Article number6921
JournalNature communications
Volume14
Issue number1
DOIs
StatePublished - Dec 2023

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy

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