Amino acid sequence alignment of the residues in and flanking the TM11 segment of various ENT homologues. Solid line above the sequences indicates the predicted extent of TM11. Numbers to the right of each sequence indicate the amino acid number of the final residue. The absolutely conserved glycines in the GXXXG motif are highlighted by the gray stripes. Species origin of sequence indicated by initial letters, m, mouse; r, rat; h, human; Ce, C. elegans; Ld, L. donavani; Pf, P. falciparum. Residues in bold in species other than P. falciparum indicate mutants studied by other laboratories and discussed in the Introduction. The bold, italicized letters in the P. falciparum sequence indicate the positions where MTS reagents reacted with Cys substitution mutants. The vertical arrow indicates the location of the F/L polymorphism at position 394 in the P. falciparum sequence.