Bacterial homolog of Na+/Cl- dependent neurotransmitter transporters
Aquifex aeolicus (thermophile, bacteria) VF5
Neurons in the brain rapidly communicate with each other in the following manner:
The rapid communication requires not only to release neurotransmitters rapidly to synaptic clefts but also to re-uptake unnecessary neurotransmitters rapidly. This procedure removes excess neurotransmitters and prepares for next signals. The re-uptake of neurotransmitters is performed by neurotransmitter sodium symporters (NSSs) and the up-taken neurotransmitters are later reused. This thermodynamically uphill transports use sodium and chloride electrochemical gradients. Substances to transport are wide, and lack of Na+/Cl--dependent transporters function causes multiple disorders, such as depression, Parkinson's disease, orthostatic intolerance and epilepsy.
The structure shown here is a bacterial homologue of Na+/Cl--dependent neurotransmitter transporters (LeuTAa) from Aquifex aeolicus complexed with a substrate (leucine), two sodium ions, a chloride ion. It consists of 12 transmembrane alpha helices, and TM1-TM5 and TM6-TM10 form similar structures. The leucine are bound to the protein core, which exists in halfway across the membrane, partially unwound helices, with hydrogen bonds. Sodium ions also exist near the core, stabilizing the ligand binding site.
Although this structure is the closed state including ligands, it is also indicative of the system of re-take which open the outer side and inner side alternately.
Protein Data Bank (PDB)
author: Sachiyo Nomura, translated by Takahiro Kudou