The SLC6/NSS family members KAAT1 and CAATCH1 have a 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).