![Figure 3. Amino acid exchange by ASCT2 is associated with transmembrane charge movement. (A) Voltage-jump protocol used in the experiment. (B) Original current traces in response to the voltage jump in the absence (red) and presence (black) of 1 mM cysteine (inset shows original currents not cut off at 0.5 nA). (C) Current trace obtained by subtraction of currents in the presence from that in the absence of cysteine. (D) Voltage dependence of the charge movement of the on-response obtained by integrating the current over time. The red line illustrates a fit of the Boltzmann equation (Q(Vm) = Qmin + Qmax · [1 + exp(ZQ(VQ − Vm) · F/(RT))]−1; Q represents the charge moved, ZQ is the valence of this charge, VQ is the midpoint potential of the charge movement, R is the gas constant, T is the temperature, and F is the Faraday constant) to the data with a zq of 0.74 and a midpoint potential of −19 mV. (E) Voltage dependence of the relaxation rate constant for decay of the transient current. The line represents a fit to the equation 1/τ = k1(0) exp(zqFV/2RT) + k2(0) exp(−zqFV/2RT), with zq = 0.41.](https://cdn.rupress.org/rup/content_public/journal/jgp/141/6/10.1085_jgp.201210948/6/jgp_201210948_fig3.jpeg?Expires=1767782536&Signature=Ke1fGj0sFR4v4F27eBmYL6JiqTdVDE3zMDmo3CbVjlY7QkdEaMOSuW6L-zdtA03EUaAVTKTkNVRbtPLEJzOkNZmyzFXVTschEGY5ZaMKXF9QoeNg4Mq41Qq8OeA~Z4AuZnWsLOtwS2w0ABBdGGYsVwU9pXRdysmGagrzkq8S2~NbKOA-QgB7hjaXRrT4PAN0ot-VLqZ5USqF~8zVIbR9AcT0z4jmUH5DKg~VizWqkXctou1~axhyblKL34iJieIIU-D~d5QD~HQq059JfydLZv7-x~J3UjlrQa~z9yIh5g5gi~Gk4WU3u~lDUBMJojBxjsJ2Y-F4AhcUPHB8dWNurw__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Amino acid exchange by ASCT2 is associated with transmembrane charge movement. (A) Voltage-jump protocol used in the experiment. (B) Original current traces in response to the voltage jump in the absence (red) and presence (black) of 1 mM cysteine (inset shows original currents not cut off at 0.5 nA). (C) Current trace obtained by subtraction of currents in the presence from that in the absence of cysteine. (D) Voltage dependence of the charge movement of the on-response obtained by integrating the current over time. The red line illustrates a fit of the Boltzmann equation (Q(Vm) = Qmin + Qmax · [1 + exp(ZQ(VQ − Vm) · F/(RT))]−1; Q represents the charge moved, ZQ is the valence of this charge, VQ is the midpoint potential of the charge movement, R is the gas constant, T is the temperature, and F is the Faraday constant) to the data with a zq of 0.74 and a midpoint potential of −19 mV. (E) Voltage dependence of the relaxation rate constant for decay of the transient current. The line represents a fit to the equation 1/τ = k1(0) exp(zqFV/2RT) + k2(0) exp(−zqFV/2RT), with zq = 0.41.
