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Bordetella pertussis BctCBA Mediates Citrate-Dependent Zn2+ and Ni2+ binding

Barreiro Chiorato, L.; Silveira Derami, M.; Aroucha de Brito, J. P.; de Souza, L. R.; Bueno, N. F.; Massirer, K. B.; Benington, M. H.; Sgro, G. G.; Marques, M. V.; Junqueira Borges, R.; Talachia Rosa, L.

2026-07-30 biochemistry
10.64898/2026.07.27.740893 bioRxiv
Show abstract

Bordetella pertussis, the causative agent of whooping cough, is a reemerging public health threat. While the Tripartite Tricarboxylate Transporter (TTT) system BctCBA was previously implicated solely in citrate uptake, we demonstrate that the solute-binding protein BctC specifically binds citrate chelated with Zn{superscript 2} and Ni{superscript 2}. To elucidate the molecular mechanism of this interaction, we determined the crystal structures of BctC in three states: apo, open, and closed (citrate-zinc-bound), defining the structural determinants for metal-citrate recognition. Comparative analyses suggest that citrate-mediated divalent cation binding is a widespread feature among bacterial TTT homologs. Finally, in silico modeling of the full BctCBA complex predicts an elevator-type transport mechanism. Together, these findings redefine the functional scope of BctCBA, revealing a sophisticated strategy by which B. pertussis exploits organic chelators to acquire essential trace metals during infection.

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