Fig. 4.

Potassium efflux from E. coli is triggered by quinones. NEM (0.5 mM), benzoquinone (BQ), menadione (MD), or duroquinone (DQ) was added to the cell suspension at a time indicated by the arrows, and potassium release was recorded by an ion-selective electrode. Strains without the Kef systems (MJF276; black) and with chromosomally encoded KefFC (MJF274; red) and MJF276 complemented with a KefFC-encoding plasmid (blue) were used. The inset shows means and standard errors of rate constants obtained by fitting of the traces from three independent measurements.