This entry represents Solute carrier family 22 members 4/5 (SLC22A4/5) and similar proteins from chordates. This protein family belong to the organic cation transporter family and to the major facilitator superfamily (MFS) of membrane transport proteins. MSF proteins are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement [, , ].SLC22A4/5 are sodium-ion dependent transporters. SLC22A4 is a low affinity carnitine transporter, highly specific for the uptake of ergothioneine (ET), a thiolated derivative of histidine with antioxidant properties. ET is a natural compound produced only by certain fungi and bacteria and must be absorbed from the diet by humans and other vetebrates [, ]. SLC22A5 is a high affinity carnitine transporter involved in the active cellular uptake of carnitine [, ].
