The SLC6 orphans are forming a family of amino acid transporters.
Transporters in the human genome are grouped in solute carrier families (SLC). The SLC6 family is one of the biggest transporter families in the human genome comprising 20 members. It is usually referred to as the neurotransmitter transporter family because its founding members encode transporters for the neurotransmitters GABA, noradrenaline, serotonin and dopamine. The family also includes a number of 'orphan' transporters, the function of which has remained elusive until recently. Identification of the broadly specific neutral amino acid transporter SLC6A19 (also called B(0)AT1) suggested that all orphan transporters may in fact be amino acid transporters. This was subsequently confirmed by the identification of SLC6A20 as the long-sought IMINO system, a proline transporter found in kidney, intestine and brain. Very recently, SLC6A15 was identified as the neutral amino acid transporter B(0)AT2. All amino acid transporters appear to cotransport only 1Na(+) together with the amino acid substrate. Both, B(0)AT1 and B(0)AT2 are chloride independent, whereas IMINO is chloride dependent. The amino acid transporters of the SLC6 family are functionally and sequence related to the recently crystallized leucine transporter from Aquifex aeolicus. The structure elegantly explains many of the mechanistic features of the SLC6 amino acid transporters.
Bröer
Stefan
S
School of Biochemistry & Molecular Biology, Building 41, Australian National University, Canberra, ACT 0200, Australia. stefan.broeer@anu.edu.au
D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000818:Animals; D015894:Genome, Human; D006801:Humans; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D050479:Neurotransmitter Transport Proteins / Q000737:chemistry / Q000502:physiology; D009928:Organ Specificity; D050480:Plasma Membrane Neurotransmitter Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D011487:Protein Conformation
D026921:Amino Acid Transport Systems, Neutral; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050479:Neurotransmitter Transport Proteins; D050480:Plasma Membrane Neurotransmitter Transport Proteins; C506212:SLC6A15 protein, human; C419411:SLC6A16 protein, human; C491436:SLC6A19 protein, human; C431703:SLC6A20 protein, human; C091048:SLC6A20 protein, rat