FIGURE 7.
EAAC1T101A is active in exchange mode, but with slowed exchange kinetics. A, typical transport current elicited by a glutamate concentration jump at time t = 0, generated by laser flash photolysis of 4 mm 4-methoxy-7-nitroindolinyl-caged glutamate. The intracellular solution contained 140 mm NaMES and 10 mm glutamate, and the extracellular solution contained 140 mm NaMES (Vm = 0 mV). The solid line is a fit with a sum of three exponential terms (time constants for the decaying phases stated; the third phase represents the rising phase, which is most likely related to glutamate binding). B, similar experiment with EAAC1WT, 1 mm 4-methoxy-7-nitroindolinyl-caged glutamate under conditions that match the fractional occupation of the glutamate binding site to that of EAAC1T101A in A.