2l5y | pdb_00002l5y
NMR structure of calcium-loaded STIM2 EF-SAM.
Structural highlights
Function[STIM2_HUMAN] Plays a role in mediating store-operated Ca(2+) entry (SOCE), a Ca(2+) influx following depletion of intracellular Ca(2+) stores. Functions as a highly sensitive Ca(2+) sensor in the endoplasmic reticulum which activates both store-operated and store-independent Ca(2+)-influx. Regulates basal cytosolic and endoplasmic reticulum Ca(2+) concentrations. Upon mild variations of the endoplasmic reticulum Ca(2+) concentration, translocates from the endoplasmic reticulum to the plasma membrane where it probably activates the Ca(2+) release-activated Ca(2+) (CRAC) channels ORAI1, ORAI2 and ORAI3. May inhibit STIM1-mediated Ca(2+) influx.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedStromal interaction molecules (STIM)s function as endoplasmic reticulum calcium (Ca(2+)) sensors that differentially regulate plasma membrane Ca(2+) release activated Ca(2+) channels in various cells. To probe the structural basis for the functional differences between STIM1 and STIM2 we engineered a series of EF-hand and sterile alpha motif (SAM) domain (EF-SAM) chimeras, demonstrating that the STIM1 Ca(2+)-binding EF-hand and the STIM2 SAM domain are major contributors to the autoinhibition of oligomerization in each respective isoform. Our nuclear magnetic resonance (NMR) derived STIM2 EF-SAM structure provides a rationale for an augmented stability, which involves a 54 degrees pivot in the EF-hand:SAM domain orientation permissible by an expanded nonpolar cleft, ionic interactions, and an enhanced hydrophobic SAM core, unique to STIM2. Live cells expressing "super-unstable" or "super-stable" STIM1/STIM2 EF-SAM chimeras in the full-length context show a remarkable correlation with the in vitro data. Together, our data suggest that divergent Ca(2+)- and SAM-dependent stabilization of the EF-SAM fold contributes to the disparate regulation of store-operated Ca(2+) entry by STIM1 and STIM2. Auto-inhibitory role of the EF-SAM domain of STIM proteins in store-operated calcium entry.,Zheng L, Stathopulos PB, Schindl R, Li GY, Romanin C, Ikura M Proc Natl Acad Sci U S A. 2011 Jan 25;108(4):1337-42. Epub 2011 Jan 7. PMID:21217057[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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