Fig. 5

Role of Lys 154 in the asymmetry of the substrate interaction. a Lys 154 forms an H bond with Gly 15 at the C-terminal end of TM 1a in the BasC holo structure. 2Fo-Fc electron density map (blue) is shown. b 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 human Asc-1 (hAsc-1) were studied. In b, data (mean ± s.e.m.) normalized to WT values from 3 independent experiments are shown. Representative kinetic experiments of either extracellular (c) or cytoplasmic (d) sides of K154A BasC mutant reconstituted in PLs. In both cases, kinetics was examined in the presence of 5 µM Nb74 to monitor only right-side-out-oriented transporters. In c, d, data (mean ± s.e.m.) correspond to quadruplicates. Eadie-Hofstee transformation of the kinetics presented in c and d is shown in the insets. Source data are provided as a Source Data file