However, PCP has little affinity for the human monoamine transporters, including the dopamine transporter (DAT). Amphetamine enantiomers are also substrates for a specific neuronal synaptic vesicle uptake transporter called VMAT2. The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites. Tianeptine has no affinity for the dopamine transporter or the dopamine receptors. SLC30A3 is the primary zinc transporter involved in cerebral zinc homeostasis. Amphetamine is also a substrate for the presynaptic vesicular monoamine transporter, . The mutation changes a single amino acid in the transporter protein SLC45A2. Some gram-positive bacteria have BPs fused to the transmembrane domain of the transporter itself. The antiporter is a heterodimeric amino acid transporter. Cocaine binds tightly at the dopamine transporter forming a complex that blocks the transporter's function. In summary, MDMA enters monoamine neurons by acting as a monoamine transporter substrate. Hartnup disease is a deficiency of the tryptophan amino acid transporter, which results in pellagra. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species. GLUT is a type of uniporter transporter protein. GLUT1 was the first glucose transporter to be characterized.