The two highly homologous amino acid transporters, KAAT1 and CAATCH1, members of the Na⁺/Cl^--dependent transporter family, give rise to specific kinds of current depending on the transported amino acid, the cotransported ion, pH and the membrane voltage which are notably distinct between the two proteins. These diversities represent useful tools in structural-functional studies. To determine whether KAAT1 and CAATCH1 form functional oligomers, we have constructed four concatameric proteins: two homo-comcatamers (K-K and C-C) and two hetero-concatamers (K-C and C-K), for electrophysiological analysis. Furthermore, eight constructs, in which the two transporters were linked to YFP or CFP in N- or C-terminus were also prepared, in order to determine the oligomer formation by FRET analysis. All the constructs are fully active and the electrophysiological behavior is consistent with the activity as monomeric proteins. The FRET studies instead demonstrate the structural oligomerization of these transporters, and in agreement to the crystallographic information from LeuTAa (a bacterial member of the family), the quantitative FRET values suggest that the C-terminals of the subunits are closer one another than the N-terminals.