Figure 5.

Concentration dependence of l-cystine (○), l-arginine (▾), and l-leucine (●) uptake by oocytes expressing the hrBAT-mb^0,+AT fusion protein. Uptake experiments were performed at five or six different amino acid concentrations, and background uptake by water-injected oocytes was subtracted. Sigmoidal curves corresponding to Michaelis-Menten kinetics were fitted to the experimental data using a nonlinear regression routine. For every concentration, data from means of 12 oocytes ± SEM pooled from two independent experiments are shown. The apparent K_m derived from the curves for l-cystine, l-arginine, and l-leucine were 41 μM, 72 μM, and 1.1 mM, respectively.