pfam18696: SMP_C2CD2L (this model, PSSM-Id:376120 is obsolete and has been replaced by 465835)
Synaptotagmin-like, mitochondrial and lipid-binding domain
This is a lipid transport domain found in phospholipid transfer proteins such as C2CD2L-like (also known as TMEM24). The TMEM24-SMP domain is shown to bind glycerolipids with a preference for phosphatidylinositol (PI).The bound PI is then transferred to the plasma membrane (PM) where it is converted to phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] to replenish pools of this lipid hydrolyzed during glucose-stimulated signaling. PI(4,5)P2 is required for Ca2+-dependent exocytosis hence, the SMP domain of TMEM24 is essential for sustaining the intracellular Ca2+ oscillations that trigger bursts of insulin granule release and hence insulin secretion. The SMP domain belongs to a superfamily of lipid/hydrophobic ligand-binding domains called TULIP for (tubular lipid-binding proteins) it adopts TULIP fold with two alpha helices and a highly curved antiparallel beta sheet forming a cornucopia-like structure.
Jiyao W et al.(2023). "The conserved domain database in 2023.",