Sequence Cluster id id2 desc organism isHeteromeric 1 Singleton1 TCDB::O67854 2.A.22.4.2 The amino acid (leucine):2 Na+ symporter, LeuTAa (Yamashita et al., 2005). LeuT possesses two ion binding sites, NA1 and NA2, both highly specific for Na+ but with differing mechanisms of binding (Noskov and Roux, 2008). X-ray structures have been determined for LeuT in substrate-free outward-open and apo inward-open states Aquifex aeolicus