FIG. 5.

Effects of zntB expression on Zn²⁺ efflux. Efflux was measured at 37°C in E. coli strains GR480 (□), RS1220 (▪), and RS1220/pAJW54 (•) as described in Materials and Methods. GR480 carries chromosomal deletions in each of the known zinc transport loci (ΔzntA, ΔzitB, ΔzupD, ΔznuABC, and ΔyiiP) but retains a functional zntB allele. RS1220 was derived from GR480 by introducing an additional mutation in zntB. Plasmid pAJW54 encodes a wild-type zntB allele from serovar Typhimurium. The data shown are the averages of three independent experiments. Variability was less than ±5% at each point. Correlation coefficients derived from linear regression analysis were >0.95 for each individual experiment.