1. SARAF Luminal Domain Structure Reveals a Novel Domain-Swapped β-Sandwich Fold Important for SOCE Modulation
- Author
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Kimberlin, Christopher R, Meshcheriakova, Anna, Palty, Raz, Raveh, Adi, Karbat, Izhar, Reuveny, Eitan, and Minor, Daniel L
- Subjects
Biochemistry and Cell Biology ,Biological Sciences ,Biotechnology ,1.1 Normal biological development and functioning ,Underpinning research ,Generic health relevance ,Calcium ,Calcium Signaling ,Crystallography ,X-Ray ,HEK293 Cells ,Humans ,Intracellular Calcium-Sensing Proteins ,Membrane Proteins ,Models ,Molecular ,Protein Conformation ,beta-Strand ,Protein Domains ,Protein Folding ,Protein Multimerization ,store-operated calcium entry (SOCE)SARAFX-ray crystallographydomain swapping ,beta-sandwich fold ,electrophysiology ,SARAF ,X‐ray crystallography ,domain swapping ,store-operated calcium entry ,β-sandwich fold ,Medicinal and Biomolecular Chemistry ,Microbiology ,Biochemistry & Molecular Biology ,Biochemistry and cell biology - Abstract
Store-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 Ca2+ stores and generate intracellular Ca2+ 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 β-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 β-strands (β9 and β10) 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. Förster 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.
- Published
- 2019