Figure 5.

Pb²⁺-dependent attenuation of total heme is largely dependent on heme synthesis. A, WT cells untreated (left) or treated (right) with 500 μm SA and the indicated concentrations of Pb²⁺ demonstrate that Pb²⁺ has a larger effect on depleting total heme in cells that can properly synthesize heme. B and C, endogenous heme, but not exogenous heme, is degraded in a Pb²⁺-dependent manner. Total (B) and labile heme (C) were measured in HS1-expressing WT or hem1Δ cells conditioned with the indicated Pb²⁺ concentration and/or 200 μm ALA or 50 μm hemin chloride during the preculture and/or post-Pb²⁺ recovery period. All data represent the mean ± S.D. (error bars) of triplicate cultures, and statistical significance was assessed using a two-sample t test. In A, black asterisks represent the statistical significance between the indicated pairwise comparisons of conditions, and red asterisks represent the statistical significance relative to 0 μm Pb for each time point. In B, black asterisks represent the statistical significance relative to 0 μm Pb for each test condition. In C, the black asterisks represent the statistical significance between the indicated pairwise comparisons of strains. *, p < 0.05; **, p < 0.01; ***, p < 0.001; n.s., not significant.