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.
Highlights
Pathogenic bacteria remove iron from the haem of host tissues and use it as a catalytic center of many enzymes
The haem degradation reaction by haem oxygenase has been well characterized at the atomic level, but less is known about the haem import reaction across the cellular membrane, which is coupled with ATP hydrolysis by the ATP-binding cassette (ABC) haem importer
Recombinant BhuUV and BhuT were separately overexpressed in E. coli and purified
Summary
Pathogenic bacteria remove iron from the haem of host tissues and use it as a catalytic center of many enzymes. 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. The HmuUV structure in a nucleotide-free form consisted of the dimerized TMD (HmuU) and dimerized NBD (HmuV) This structure showed that the haem translocation pathway through HmuU is open toward the periplasmic side and is closed facing the cytoplasmic side, suggesting that HmuUV in this state is in an outward-facing conformation. In combination with previous HmuUV studies, this structural study provides mechanistic insights into the conformational transitions of the bacterial haem importer during its reaction cycle
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
