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. Author manuscript; available in PMC: 2013 Mar 17.
Published in final edited form as: Nat Chem Biol. 2012 Jul 8;8(8):731–736. doi: 10.1038/nchembio.1020

Figure 4. Catecholate siderophores and yersiniabactin exert opposing effects on copper cytotoxicity.

Figure 4

(a) Growth of wild type (UTI89), yersiniabactin (ΔybtS), catecholate siderophore (ΔentB), or total siderophore (ΔentBΔybtS) expression mutants in the presence of copper was determined. Results were consistent with copper-dependent cytoprotective effect for yersiniabactin and cytotoxic effect for catecholate siderophores. (b) Exogenous addition of 20 μM of the siderophore enterobactin, or its catecholate moiety 2,3-dihydroxybenzoate (DHB) enhances copper (II) sulfate toxicity in UTI89. (c) Apo-yersiniabactin prevents catechol-dependent reduction of copper (II) sulfate to copper (I) in an order-of-addition dependent manner. The complete reaction system consisted of 17.5 μM copper(II) sulfate, either 20 μM enterobactin (ent) or its catecholate moiety 2,3-dihydroxybenzoic acid (DHB), 25 μM apo-yersiniabactin (Ybt), and 25 μM of the copper(I) indicator bathocuproine sulfonate. Reagents were added in the order indicated and Cu(I)-bathocuproine absorbance was determined 30 min after addition of the last reagent. Results were confirmed in three independent experiments.