4RM6: Crystal Structure Of Hemopexin Binding Protein

Haemophilus influenzae is an obligate human commensal/pathogen that requires haem for survival and can acquire it from several host haemoproteins, including haemopexin. The haem transport system from haem-haemopexin consists of HxuC, a haem receptor, and the two-partner-secretion system HxuB/HxuA. HxuA, which is exposed at the cell surface, is strictly required for haem acquisition from haemopexin. HxuA forms complexes with haem-haemopexin, leading to haem release and its capture by HxuC. The key question is how HxuA liberates haem from haemopexin. Here, we solve crystal structures of HxuA alone, and HxuA in complex with the N-terminal domain of haemopexin. A rational basis for the release of haem from haem-haemopexin is derived from both in vivo and in vitro studies. HxuA acts as a wedge that destabilizes the two-domains structure of haemopexin with a mobile loop on HxuA that favours haem ejection by redirecting key residues in the haem-binding pocket of haemopexin.
PDB ID: 4RM6Download
MMDB ID: 139250
PDB Deposition Date: 2014/10/20
Updated in MMDB: 2016/06
Experimental Method:
x-ray diffraction
Resolution: 1.6  Å
Source Organism:
Similar Structures:
Biological Unit for 4RM6: monomeric; determined by author and by software (PISA)
Molecular Components in 4RM6
Label Count Molecule
Protein (1 molecule)
Heme/hemopexin-binding Protein(Gene symbol: hxuA)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

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