H(+)-myo-inositol cotransporter and similar transporters of the Major Facilitator Superfamily
This subfamily is composed of myo-inositol/inositol transporters and similar transporters from vertebrates, plant, and fungi. The human protein is called H(+)-myo-inositol cotransporter/Proton myo-inositol cotransporter (HMIT), or H(+)-myo-inositol symporter, or Solute carrier family 2 member 13 (SLC2A13). HMIT is classified as a Class 3 GLUT (glucose transporter) based on sequence similarity with GLUTs, but it does not transport glucose. It specifically transports myo-inositol and is expressed predominantly in the brain, with high expression in the hippocampus, hypothalamus, cerebellum and brainstem. HMIT may be involved in regulating processes that require high levels of myo-inositol or its phosphorylated derivatives, such as membrane recycling, growth cone dynamics, and synaptic vesicle exocytosis. Arabidopsis Inositol transporter 4 (AtINT4) mediates high-affinity H+ symport of myo-inositol across the plasma membrane. The HMIT-like subfamily belongs to the Glucose transporter -like (GLUT-like) family 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.
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