Abstract
STIM1 and STIM2 are widely expressed endoplasmic reticulum (ER) Ca 2+ sensor proteins able to translocate within the ER membrane to physically couple with and gate plasma membrane Orai Ca 2+ channels. Although they are structurally similar, we reveal critical differences in the function of the short STIM-Orai-activating regions (SOAR) of STIM1 and STIM2. We narrow these differences in Orai1 gating to a strategically exposed phenylalanine residue (Phe-394) in SOAR1, which in SOAR2 is substituted by a leucine residue. Remarkably, in full-length STIM1, replacement of Phe-394 with the dimensionally similar but polar histidine head group prevents both Orai1 binding and gating, creating an Orai1 non-agonist. Thus, this residue is critical in tuning the efficacy of Orai activation. While STIM1 is a full Orai1-agonist, leucine-replacement of this crucial residue in STIM2 endows it with partial agonist properties, which may be critical for limiting Orai1 activation stemming from its enhanced sensitivity to store-depletion.
Original language | English |
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Article number | 3183 |
Pages (from-to) | 3183 |
Journal | Nature Communications |
Volume | 5 |
DOIs | |
State | Published - Feb 4 2014 |
Keywords
- Amino Acid Sequence
- Binding Sites
- Calcium Channels/metabolism
- Cell Adhesion Molecules/chemistry
- Humans
- Membrane Proteins/chemistry
- Molecular Sequence Data
- Neoplasm Proteins/chemistry
- ORAI1 Protein
- Sequence Homology, Amino Acid
- Stromal Interaction Molecule 1
- Stromal Interaction Molecule 2