Table 1. Table 1. Characteristics of biochemically characterized NATs.

All NATs shown are high-affinity transporters recognizing their physiological substrate at the low μΜ range, except UacT which is low affinity transporter. NATs marked with an (*) can be modeled, with 100% probability, on the crystal structure of UapA or UraA conforming to the 7+7 inverted repeat fold 30. 5-FU is 5-fluorouracil. Consensus sequences of three motifs involved in function and specificity are shown. Notice that the most significant differences in the NAT signature motif of nucleobase versus L-ascorbate transporters concern substitutions of the aromatic Phe/Tyr at position 2 and of the polar Gln/Glu with a Pro. ?, not tested. ^#S. Frillingos pers. com.