RT Journal Article
SR Electronic
T1 Cryo-EM Structure of a Ferrichrome Importer FhuCDB
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.06.15.448540
DO 10.1101/2021.06.15.448540
A1 Wenxin Hu
A1 Hongjin Zheng
YR 2021
UL http://biorxiv.org/content/early/2021/06/15/2021.06.15.448540.abstract
AB As one of the most elegant biological processes developed in bacteria, the siderophore-mediated iron uptake demands the action of specific ATP-binding cassette (ABC) importers. Although extensive studies have been done on various ABC importers, the molecular basis of these iron-chelated-siderophore importers are still not fully understood. Here, we report the structure of a ferrichrome importer FhuCDB from Escherichia coli at 3.4Å resolution determined by cryo electron microscopy. The structure revealed a monomeric membrane subunit of FhuB with a substrate translocation pathway in the middle. In the pathway, there were unique arrangements of residues, especially layers of methionines. Important residues found in the structure were interrogated by mutagenesis and functional studies. Surprisingly, the importer’s ATPase activity was decreased upon FhuD binding, which deviated from the current understanding about bacterial ABC importers. In summary, our studies not only reveal a new structural twist in the type II ABC importer subfamily, but also provide biological insights in the transport of iron-chelated siderophores.Competing Interest StatementThe authors have declared no competing interest.