FIGURE 4.
Functional expression of AMT1;1-Q57H mutant in oocytes. A, AMT1;1 showed saturation kinetics for NH4+-induced currents with a Km for ammonium of 34 ± 7 μm (n = 14), whereas the currents mediated by AMT1;1-Q57H did not saturate in the range tested (force fit to Michaelis-Menten kinetics yielded a Km = 2.2 ± 0.4 mm; n = 13). B, shown are the inward currents from different oocytes injected with water (H2O) or the cRNA from AMT1;1 (wild type) and the mutant AMT1;1-Q57H (Q57H). The original recordings show the currents induced with 1 mm of chloride salts of the different cations (indicated by the lines). Oocytes were clamped at −120 mV. Similar results were obtained from six oocytes.