Table 2.

Function of STIM1 and STIM2 protein domains.

Domain	Function
EF-hand	ER Ca2+ sensor
SAM	Protein interaction domain. When ER Ca2+ stores are full, maintains STIM in folded conformation Upon Ca2+ store-depletion, facilitates STIM oligomerization
CC1-CC3	ER retention and stability Under-store replete conditions, inhibitory helix in CC1 keeps STIM in inactive conformation Under store-deplete conditions, elongates to facilitate interaction with Orai1
SOAR (within CC2-CC3)	Minimal region required for Orai1 activation
K-rich	Initial recruitment of STIM to ER-PM junction STIM1 gating of TRPC channels Electrostatic interactions with PM phospholipids