Plant organic cation/carnitine transporters of the Major Facilitator Superfamily of transporters
Plant organic cation/carnitine transporters (OCTs) are sequence-similar to their animal counterparts, which are broad-specificity transporters that play a critical role in the excretion and distribution of endogeneous organic cations and for the uptake, elimination and distribution of cationic drugs, toxins, and environmental waste products. Little is know about plant OCTs. In Arabidopsis, there are six genes belonging to this family that show distinct, organ-specific expression pattern of the individual genes. AtOCT1 has been found to affect root development and carnitine-related responses in Arabidopsis. AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT5 and 6 during salt stress treatments. Plant OCTs belongs to the Solute carrier 22 (SLC22) family of organic cation/anion/zwitterion transporters of the Major Facilitator Superfamily (MFS) of membrane transport proteins. MFS proteins 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.",