Fig. 3

Structure of the amino acid binding site and substrate-induced fitting. a View of the bound 2-AIB ligand, showing the POLDER electron density map contoured at 3σ, dark red. Distances between atoms of the substrate and BasC residues compatible with H bonds are indicated (dashed lines). b 10 μM [³H]l-alanine exchange (pmol μg protein⁻¹ s⁻¹) into BasC PLs containing 4 mM of the indicated compounds. c Binding of 2-AIB displaces Gly 19 in the BasC apo structure (light gray) to H bond distance (dashed line) with Ser 282 in the holo structure (rainbow). d 10 µM [³H]l-alanine/4 mM l-alanine exchange by BasC reconstituted in proteoliposomes (PLs) (black bars) and transport of 10 µM [³H]l-alanine in HeLa cells by human Asc-1 (hAsc-1) (gray bars). Wild-type (WT) and the indicated homologous mutants of BasC and hAsc-1 were studied. Transport is normalized to the corresponding wild-type values. In b, d, data (mean ± s.e.m.) from 3 independent experiments are shown. Source data are provided as a Source Data file