The Solute Carrier 1A (SLC1A) transporter family are membrane bound amino acid transporters which possess a unique dual transport and chloride channel function. Substrate selectivity and ion coupling is diverse across the family despite relatively high levels of sequence identity, particularly in substrate and ion binding pockets. The excitatory amino acid transporters (EAATs) are concentrative glutamate transporters which are vital in the control of synaptic glutamate concentrations throughout the brain and key to the prevention of excitotoxic events (Danbolt, 2001). The EAATs couple the transport of one glutamate to 3Na+ and a proton followed by the counter-transport of one K+ required to prepare the transporter for further substrate binding (Zerangue & Kavanaugh, 1996b). Interestingly, some family members such as EAAT2 from Drosophila Melanogaster (dEAAT2) do not retain K+ or H+ coupling.
Using electrophysiology and radiolabelled uptake techniques, we have explored the molecular basis which underlies K+ coupling in the SLC1A family. Our results shed light on how differences in ion coupling mechanisms manifest in distinct members of the SLC1A family and also how differential coupling can lead to transport or exchange modes.