Crystal structure of bacterial haem importer complex in the inward-facing conformation

Nat Commun. 2016 Nov 10:7:13411. doi: 10.1038/ncomms13411.

Abstract

Pathogenic bacteria remove iron from the haem of host tissues and use it as a catalytic center of many enzymes. Haem uptake by pathogenic bacteria is facilitated by the membrane-integrated haem importer, which belongs to the type II ATP-binding cassette (ABC) transporter. Here we present crystal structures of Burkholderia cenocepacia haem importer BhuUV complexed with the periplasmic haem-binding protein BhuT and in the absence of BhuT. The transmembrane helices of these structures show an inward-facing conformation, in which the cytoplasmic gate of the haem translocation pathway is completely open. Since this conformation is found in both the haem- and nucleotide-free form, the structure of BhuUV-T provides the post-translocation state and the missing piece in the transport cycle of the type II importer. Structural comparison with the outward-facing conformation reported for the haem importer ortholog HmuUV from Yersenia pestis gives mechanistic insights into conformational transitions and haem secretion during the haem transport cycle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biological Transport
  • Burkholderia cenocepacia / genetics
  • Burkholderia cenocepacia / metabolism
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Crystallography, X-Ray
  • Heme / chemistry
  • Heme / metabolism*
  • Heme-Binding Proteins
  • Hemeproteins / chemistry
  • Hemeproteins / genetics
  • Hemeproteins / metabolism
  • Models, Molecular
  • Periplasm / metabolism*
  • Protein Conformation
  • Sequence Homology, Amino Acid

Substances

  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Carrier Proteins
  • Heme-Binding Proteins
  • Hemeproteins
  • Heme