FIGURE 6.

Effect of gramicidin on the proton flux assay. Vesicles containing gramicidin were prepared in a manner similar to M2 containing vesicles. The final concentration of gramicidin was 0, 5, 50, or 500 (not shown) ng/mL. (Upper curve) Protein-free control shows no valinomycin signal. (Middle curve) At 5 ng/mL gramicidin, compared to control, twice the slope was observed after addition of valinomycin. There was also a reduced total signal, suggesting potassium leakage through gramicidin. (Lower curve) Gramicidin at a concentration of 50 ng/mL was sufficient to eliminate any response to valinomycin and CCCP. Higher concentrations also showed no signal (data not shown). Arrows and arrowheads have the same significance as in Fig. 3.