FIGURE 4.

Sensitivity of S359C mutants to CuPh. A, HeLa cells expressing the indicated mutants were preincubated in NaCl-containing medium supplemented with the indicated concentrations of CuPh for 5 min at room temperature. Subsequently, the cells were washed and assayed for [³H]GABA transport as described under “Experimental Procedures.” Inset, the abscissa is expanded, to show the effects of CuPh on S359C/K448A and S359C/K448C at submicromolar concentrations of the oxidant. B, HeLa cells expressing the indicated mutants were incubated with or without 30 μm CuPh prior to the transport measurement. Values are given as a percentage of activity in the absence of CuPh. The data are expressed as a percentage of untreated control and represent mean ± S.E. (error bars). The transport activity of the non-treated mutants (percentage of WT) was 21.3 ± 1.1% (n = 22) for S359C and 17 ± 4, 14 ± 4, and 58 ± 7% (n = 3) for S359C/K448G, S359C/K448E, and S359C/K448Q, respectively (*, p < 0.05).