Fig. 8: Fur causes iron atoms cell^-1 to decline in Co^II matching MncA-predicted availabilities.

a Total iron atoms cell⁻¹ determined by ICP-MS of cell digests, declines in cells grown in medium supplemented with high Co^II (left panel). This is consistent with the decline in intracellular Fe^II availability estimated from the residuals in Fig. 6a, calculated using Supplementary Data 5 and shown in Fig. 6b. Elevated Ni^II does not affect total iron atoms cell⁻¹ (right panel). Total iron cell⁻¹ is less in ∆fur but does not further decline in elevated Co^II. The decline in iron cell⁻¹ in response to elevated Co^II is Fur-dependent. b Fur binds Co^II to promote DNA-binding: simulated using known Co^II affinity of Fur, DNA affinity of Co^II-Fur, plus apo-Fur DNA affinity and Fur molecules cell⁻¹, as simulated for Fe^II-Fur²³. Fur promoters will be aberrantly repressed in 300 µM cobalt (square and blue arrow) causing the predicted decline in intracellular available Fe^II shown in Fig. 6b and observed decline in total iron atoms cell⁻¹ in panel (a). c Total manganese atoms cell⁻¹ increase in high Co^II consistent with slightly increased intracellular available Mn^II, modellable from the remaining residuals in high Co^II in Fig. 6c, calculated using Supplementary Data 5, shown in Supplementary Fig. 16b. These effects of cobalt on Mn^II are independent of Fur. Total manganese atoms cell⁻¹ decrease in high Ni^II, this trend is more pronounced in ∆mntR (Supplementary Fig. 17), the trend is not evident in ∆fur which contains low manganese (right). An analogous decrease in available intracellular Mn^II calculable (Supplementary Data 5) from the remaining residuals in high Ni^II, Fig. 6b, is shown in Supplementary Fig. 16a. Use of MncA as a probe of relative intracellular metal availabilities iteratively refines values shown in Supplementary Fig. 16, included in Supplementary Data 6−8, and provided as blueprints to assist manipulation of the speciation of in vivo protein metalation. Mean ± SD of n = 3 independent biological replicates (squares, circles, triangles) in (a) and (c). Source data are provided as a Source Data file.