Protein spinster and spinster homologs of the Major Facilitator Superfamily of transporters
The protein spinster family includes Drosophila protein spinster, its vertebrate homologs, and similar proteins. Humans contain three homologs called protein spinster homologs 1 (SPNS1), 2 (SPNS2), and 3 (SPNS3). Protein spinster and its homologs may be sphingolipid transporters that play central roles in endosomes and/or lysosomes storage. SPNS2 is also called sphingosine 1-phosphate (S1P) transporter and is required for migration of myocardial precursors. S1P is a secreted lipid mediator that plays critical roles in cardiovascular, immunological, and neural development and function. The spinster-like family belongs to the Major Facilitator Superfamily (MFS) of membrane transport proteins, which are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement.
Feature 1:putative chemical substrate binding pocket [chemical binding site]
Evidence:
Comment:based on the structures of MFS transporters with bound substrates, substrate analogs, and/or inhibitors
Comment:since MFS proteins facilitate the transport of many different substrates including ions, sugar phosphates, drugs, neurotransmitters, nucleosides, amino acids, and peptides, the residues involved in substrate binding may not be strictly conserved among superfamily members
Comment:the substrate binding site or translocation pore has access to both sides of the membrane in an alternating fashion through a conformational change of the MFS transporter
Jiyao W et al.(2023). "The conserved domain database in 2023.",