FIGURE 3.
Effect of MTS reagents on I-V relationship shape. A, shown is the mean rectification ratio (calculated as described under “Experimental Procedures”) for cys-less and each of the mutants used in the present study measured under control conditions for currents activated by PKA (20 nm), ATP (1 mm), and PPi (2 mm). Asterisks indicate a significant difference from cys-less (p < 0.05). B, shown is the effect of internal MTSET (white bars) or MTSES (black bars) on the rectification ratio in each channel variant. Asterisks indicate a significant difference from cys-less (p < 0.05). C, shown are mean rectification ratios for selected channel variants under control conditions and after modification with charged MTS reagents, plotted as a function of predicted side chain (−1 with MTSES, 0 control, and +1 with MTSET). Asterisks indicate a significant difference from the corresponding rectification ratio under control conditions (p < 0.05). Data are the means from 3–8 patches. Where no error bars are visible, these are smaller than the size of the symbol.