FIG. 2.

Topology of ENT transporters and identification of functionally important residues. Numbered rectangles represent the 11 predicted TMDs, “IN” and “OUT” designate the inside and outside of the plasma membrane, respectively, and the gray background represents the plasma membrane. Functionally important amino acids (single-letter code) are underlined and lines designate their approximate positions within TMDs. Each residue and its corresponding number reflects the particular ENT with which the study was performed as follows: M33, hENT1; C140, rENT2; G179, hENT1; G183, LdNT1.1; C337, LdNT1.1; D389, LdNT2; R393, LdNT2. Appropriate references are given in the text.