Differential roles of the C and N termini of Orai1 protein in interacting with stromal interaction molecule 1 (STIM1) for Ca2+ release-activated Ca2+ (CRAC) channel activation

J Biol Chem. 2013 Apr 19;288(16):11263-72. doi: 10.1074/jbc.M113.450254. Epub 2013 Feb 27.


The entry of extracellular Ca(2+), which is mediated by Ca(2+) release-activated Ca(2+) (CRAC) channels, is essential for T cell activation and the normal functioning of other immune cells. Although the molecular components of CRAC channels, the Orai1 pore-forming subunit and the STIM1-activating subunit have been recently identified, the gating mechanism by which Orai1 channels conduct Ca(2+) entry upon Orai1-STIM1 interaction following Ca(2+) store release remains elusive. Herein, we show that C-terminal truncations or point mutations prevented Orai1 from binding to STIM1 and subsequent channel opening. In contrast, an Orai1 mutant with an N-terminal truncation interacted with but failed to be activated by STIM1. Moreover, Orai1 channels with C-terminal disruption, but not N-terminal truncation, could be gated by fused functional domains of STIM1. Interestingly, the channel activities of Orai1 mutants carrying either an N-terminal or a C-terminal truncation were restored by a methionine mutation at the putative gating hinge, the conserved Gly-98 site in the first transmembrane segment (TM1) of Orai1. Collectively, these results support a stepwise gating mechanism of STIM1-operated Orai1 channels; the initial binding between STIM1 and the C terminus of Orai1 docks STIM1 onto the N terminus of Orai1 to initiate conformational changes of the pore-lining TM1 helix of Orai1, leading to the opening of the channel.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • HEK293 Cells
  • Humans
  • Ion Channel Gating / physiology*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mutation
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • ORAI1 Protein
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Stromal Interaction Molecule 1


  • Calcium Channels
  • Membrane Proteins
  • Neoplasm Proteins
  • ORAI1 Protein
  • ORAI1 protein, human
  • STIM1 protein, human
  • Stromal Interaction Molecule 1
  • Calcium