FIG. 5.

Effects of chelating agents on TPP⁺ uptake. As control experiments, EDTA (a) or BAPTA (b) was added at a final concentration of 1 mM to untreated cells at the time indicated by the arrow. (c) After E. coli cells were preincubated with 0.5 mM MgCl₂ for 3 min, BAPTA and EDTA were, respectively, added at a final concentration of 1 mM at the times indicated by the first and second arrows. The cells were preincubated with 0.5 mM ethylenediamine (d) or 0.5 mM spermine (e) for 3 min, and EDTA (final concentration, 1 mM) was added at the time indicated by the arrow. EDTA and BAPTA were adjusted to pH 7.2 using Tris.