Substrate specificity of MagT1 following application of test cations, 2.0 mM, in the absence of external Mg2+. For clarity, only Mg2+,Cu2+, Mn2+, and Sr2+ are represented in panel A. Oocytes were clamped at a holding potential of -15 mV and stepped from -150 mV to +25 mV in 25 mV increments for 2 s for each of the cations. Values are mean ± SEM of currents measured at the end of each voltage sweep for the respective divalent cation. B, summary of permeabilities of the tested divalent cations. Figure illustrates average permeability ratios (Erev for tested cation relative to Erev for Mg2+) given in Fig. 9A.