Fig. 2

Alignment of SLC38A9 protein homologs from four animal species and phylogenetic tree of SLC38 proteins. a Multiple sequence alignment of animal SLC38A9 homologs in zebrafish (Slc38a9: NP_001073468), humans (SLC38A9: AAI01363), mice (Slc38a9: GenBank accession number NP_848861), and planarians (Dr-SLC38A9: LC225747) showed several conserved amino acid residues. Black boxes indicate residues that were identical in all aligned proteins. Gray backgrounds indicate residues that were identical in three aligned proteins. Blue lines, transmembrane regions; brown lines, loops bound to Fab; red underline, WNTMM anchor motif; orange circles, GTS conserved motif; magenta asterisks, residues bonded with TM1a; blue triangles, residues involved in Arg binding; black circles, disulfide bonds between loops 3–4 and loops 7–8. b Phylogenetic tree of human SLC38 proteins (SLC38A1: GenBank accession number NP_001070952, SLC38A2: NP_061849, SLC38A3: NP_006832, SLC38A4: NP_001137296, SLC38A5: NP_277053, SLC38A6: NP_722518, SLC38A7: NP_001356537, SLC38A8: NP_001073911, SLC38A9: NP_001336311, SLC38A10: NP_001033073, SLC38A11: NP_001186077), the planarian Schmidtea mediterranea (S. mediterranea_slc38a-1: AKN21660, S. mediterranea_slc38a-2: AKN21661, S. mediterranea_slc38a-3: AKN21662, S. mediterranea_slc38a-4: AKN21663, S. mediterranea_slc38a-5: AKN21664, S. mediterranea_slc38a-6: AKN21665) [28], and Dr-SLC38A9 of the planarian Dugesia ryukyuensis, constructed using the neighbor-joining method [29]