Pathogenic siderophore ABC importer YbtPQ adopts a surprising fold of exporter

Abstract

and substrate-bound states by cryo-electron microscopy. YbtPQ does not adopt any known fold of ABC importers but surprisingly adopts the fold of type IV ABC exporters. To our knowledge, it is the first time an exporter fold of ABC importer has been reported. We have also observed two unique features in YbtPQ: unwinding of a transmembrane helix in YbtP upon substrate release and tightly associated nucleotide-binding domains without bound nucleotides. Together, our study suggests that siderophore ABC importers have a distinct transport mechanism and should be classified as a separate subfamily of ABC importers.

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