The SLC6/NSS family members KAAT1 and CAATCH1 have weak chloride dependence

KAAT1 and CAATCH1 are amino acid transporters cloned from the intestine of the lepidoptera Manduca sexta.(1,2) They are members of the SLC6/NSS family, which groups membrane proteins that use Na+, K+ and Cl- gradients for the coupled transport of amines and amino acids. The report of the atomic-resolution x-ray crystal structure of the eubacterium Aquifex aeolicus leucine transporter (AaLeuT)(3) has contributed significantly to understanding of the structure-function relationship in NSS proteins. Transport by AaLeuT is Cl- independent, whereas many neurotransmitter: sodium symporters like serotonin transporter (SERT), GABA transporter (GAT1), dopamine transporter and norephinephrine transporter, among others, are strongly Cl- dependent.(4)