2OVI

Structure of the Heme Binding Protein ChuX


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.213 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Structure and heme binding properties of Escherichia coli O157:H7 ChuX.

Suits, M.D.Lang, J.Pal, G.P.Couture, M.Jia, Z.

(2009) Protein Sci. 18: 825-838

  • DOI: 10.1002/pro.84

  • PubMed Abstract: 
  • For many pathogenic microorganisms, iron acquisition from host heme sources stimulates growth, multiplication, ultimately enabling successful survival and colonization. In gram-negative Escherichia coli O157:H7, Shigella dysenteriae and Yersinia ente ...

    For many pathogenic microorganisms, iron acquisition from host heme sources stimulates growth, multiplication, ultimately enabling successful survival and colonization. In gram-negative Escherichia coli O157:H7, Shigella dysenteriae and Yersinia enterocolitica the genes encoded within the heme utilization operon enable the effective uptake and utilization of heme as an iron source. While the complement of proteins responsible for heme internalization has been determined in these organisms, the fate of heme once it has reached the cytoplasm has only recently begun to be resolved. Here we report the first crystal structure of ChuX, a member of the conserved heme utilization operon from pathogenic E. coli O157:H7 determined at 2.05 A resolution. ChuX forms a dimer which remarkably given low sequence homology, displays a very similar fold to the monomer structure of ChuS and HemS, two other heme utilization proteins. Absorption spectral analysis of heme reconstituted ChuX demonstrates that ChuX binds heme in a 1:1 manner implying that each ChuX homodimer has the potential to coordinate two heme molecules in contrast to ChuS and HemS where only one heme molecule is bound. Resonance Raman spectroscopy indicates that the heme of ferric ChuX is composed of a mixture of coordination states: 5-coordinate and high-spin, 6-coordinate and low-spin, and 6-coordinate and high-spin. In contrast, the reduced ferrous form displays mainly a 5-coordinate and high-spin state with a minor contribution from a 6-coordinate and low-spin state. The nu(Fe-CO) and nu(C-O) frequencies of ChuX-bound CO fall on the correlation line expected for histidine-coordinated hemoproteins indicating that the fifth axial ligand of the ferrous heme is the imidazole ring of a histidine residue. Based on sequence and structural comparisons, we designed a number of site-directed mutations in ChuX to probe the heme binding sites and dimer interface. Spectral analysis of ChuX and mutants suggests involvement of H65 and H98 in heme coordination as mutations of both residues were required to abolish the formation of the hexacoordination state of heme-bound ChuX.


    Organizational Affiliation

    Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Hypothetical protein chuX
A, B, C, D
164Escherichia coli O157:H7Mutation(s): 0 
Find proteins for Q8X5N5 (Escherichia coli O157:H7)
Go to UniProtKB:  Q8X5N5
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.213 
  • Space Group: P 41
Unit Cell:
Length (Å)Angle (°)
a = 76.560α = 90.00
b = 76.560β = 90.00
c = 140.864γ = 90.00
Software Package:
Software NamePurpose
ADSCdata collection
PDB_EXTRACTdata extraction
HKL-2000data reduction
DENZOdata reduction
SCALEPACKdata scaling
SOLVEphasing
CNSrefinement
RESOLVEphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2008-02-12
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2017-10-18
    Type: Refinement description
  • Version 1.3: 2017-10-25
    Type: Author supporting evidence