Synaptotagmin-like mitochondrial-lipid-binding domain (IPR031468)

Short name: SMP_LBD

Overlapping homologous superfamilies


Domain relationships


Membrane contacts sites (MCSs), regions where two organelles come in close proximity to one another, act as molecular hubs for the exchange of small molecules (e.g. lipids) and signals (e.g. calcium ions). Synaptotagmin-like Mitochondrial lipid-binding Proteins (SMP) domains are exclusively found at MCSs between different organelles such as endoplasmic reticulum (ER)- Mitochondrion, ER-Plasma membrane (PM) and Nucleus-Vacuole junctions. The SMP domain is able to homo- or heterodimerize, harbors lipids in a hydrophobic cavity and mediates lipid transfer between the two adjacent bilayers independently of membrane fusion and fission reactions. SMP proteins are widespread amongst eukaryotic species with a particular enrichment in plants and features suggestive of species-specific functional variations. SMP domain- containing proteins have been classified into four broad groups: C2 domain synaptotagmin-like, PH domain-containing HT-008, PDZK8 and mitochondrial protein families [PMID: 16449791, PMID: 26686281, PMID: 28363589, PMID: 24847877, PMID: 29097544, PMID: 28479252].

The SMP domain consists of 6 beta-strands and 3 helices arranged to form a barrel whose interior is lined almost exclusively by hydrophobic residues. The resulting elongated barrel-shaped cylindrical structure harbors a lateral opening and a central hydrophobic cavity where phospholipids can bind. It dimerizes in an anti-parallel fashion to form a cylinder traversed by a deep hydrophobic groove [PMID: 24847877, PMID: 29097544, PMID: 28479252]. The SMP domain belongs to the TULIP (for TUbular LIPid-binding) protein superfamily of lipid transfer proteins [PMID: 21787343].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0008289 lipid binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles