SMP is a proposed lipid-binding module, ie a synaptotagmin-like mitochondrial-lipid-binding domain found in eukaryotes. The SMP domain has a beta-barrel structure like protein modules in the tubular-lipid-binding (TULIP) superfamily. It dimerizes to form an approximately 90-Angstrom-long cylinder traversed by a channel lined entirely with hydrophobic residues. The following two C2 domains then form arched structures flexibly linked to the SMP domain. The SMP domain is a lipid-binding domain that links the ER with other lipid bilayer-membranes within the cell.
Jiyao W et al.(2023). "The conserved domain database in 2023.",