3.A.1.21.1
The Fe³⁺-Yersiniabactin uptake transporter, YbtPQ (Brem et al., 2001; Fetherston et al., 1999). YbtPQ is a virulence factor in the highly inflammatory microenvironment characteristic of high-titer cystitis in E. coli (Koh et al. 2016). The E. coli and Y. pestis YbtP proteins are 99.7% identical. Multiple structures of the yersiniabactin importer YbtPQ from uropathogenic Escherichia coli (UPEC) have been solved in inward-open conformations of both apo and substrate-bound states by cryo-EM (Wang et al. 2020). YbtPQ does not adopt a known fold of typical ABC importers, but instead exhibits the fold of an ABC exporter. It has two unique features: unwinding of a transmembrane helix in YbtP upon substrate release and tightly associated nucleotide-binding domains without bound nucleotides (Wang et al. 2020). This ABC porter is similar to FrpBC of Vibrio anguillarum (Lages et al. 2022).