6o2v
From Proteopedia
Crystal structure of the SARAF luminal domain Cys-lock mutant monomer
Structural highlights
Function[SARAF_HUMAN] Negative regulator of store-operated Ca(2+) entry (SOCE) involved in protecting cells from Ca(2+) overfilling. In response to cytosolic Ca(2+) elevation after endoplasmic reticulum Ca(2+) refilling, promotes a slow inactivation of STIM (STIM1 or STIM2)-dependent SOCE activity: possibly act by facilitating the deoligomerization of STIM to efficiently turn off ORAI when the endoplasmic reticulum lumen is filled with the appropriate Ca(2+) levels, and thus preventing the overload of the cell with excessive Ca(2+) ions.[1] Publication Abstract from PubMedStore-Operated Calcium Entry (SOCE) plays key roles in cell proliferation, muscle contraction, immune responses, and memory formation. The coordinated interactions of a number of proteins from the plasma and endoplasmic reticulum membranes control SOCE to replenish internal Ca(2+) stores and generate intracellular Ca(2+) signals. SARAF, an endoplasmic reticulum resident component of the SOCE pathway having no homology to any characterized protein, serves as an important brake on SOCE. Here, we describe the X-ray crystal structure of the SARAF luminal domain, SARAFL. This domain forms a novel 10-stranded beta-sandwich fold that includes a set of three conserved disulfide bonds, denoted the "SARAF-fold." The structure reveals a domain-swapped dimer in which the last two beta-strands (beta9 and beta10) are exchanged forming a region denoted the "SARAF luminal switch" that is essential for dimerization. Sequence comparisons reveal that the SARAF-fold is highly conserved in vertebrates and in a variety of pathologic fungi. Forster resonance energy transfer experiments using full-length SARAF validate the formation of the domain-swapped dimer in cells and demonstrate that dimerization is reversible. A designed variant lacking the SARAF luminal switch shows that the domain swapping is essential to function and indicates that the SARAF dimer accelerates SOCE inactivation. SARAF Luminal Domain Structure Reveals a Novel Domain-Swapped beta-Sandwich Fold Important for SOCE Modulation.,Kimberlin CR, Meshcheriakova A, Palty R, Raveh A, Karbat I, Reuveny E, Minor DL Jr J Mol Biol. 2019 May 11. pii: S0022-2836(19)30263-3. doi:, 10.1016/j.jmb.2019.05.008. PMID:31082439[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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