FIGURE 6.
F179C mutation increases the Km but not the Ki value for GlcUA. A, concentration-dependent uptake of NANA (filled symbols) and GlcUA (GlcA; open symbols) by Cys-less (circles) and F179C (triangles) sialin. Values for NANA uptake by Cys-less sialin are also presented in Fig. 2. B, broad range plot of F179C-mediated uptake of GlcUA. C, summary of Km and Ki and Vmax measurements for Cys-less and F179C-mediated transport of NANA and GlcUA. Km and Vmax values were calculated from Michaelis-Menten plots, and Ki values were calculated from IC50 plots using the Cheng-Prusoff equation. For all experiments, uptake was measured for 2 min. Km, Vmax, and Ki values were calculated from four independent experiments and are presented as the mean ± S.E.