1RQ4

Crystallographic Analysis of the Interaction of Nitric Oxide with Quaternary-T Human Hemoglobin, HEMOGLOBIN EXPOSED TO NO UNDER AEROBIC CONDITIONS


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.11 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.201 

Starting Model: experimental
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This is version 1.5 of the entry. See complete history


Literature

Crystallographic analysis of the interaction of nitric oxide with quaternary-T human hemoglobin.

Chan, N.L.Kavanaugh, J.S.Rogers, P.H.Arnone, A.

(2004) Biochemistry 43: 118-132

  • DOI: https://doi.org/10.1021/bi030172j
  • Primary Citation of Related Structures:  
    1RPS, 1RQ3, 1RQ4, 1RQA

  • PubMed Abstract: 

    In addition to interacting with hemoglobin as a heme ligand to form nitrosylhemoglobin, NO can react with cysteine sulfhydryl groups to form S-nitrosocysteine or cysteine oxides such as cysteinesulfenic acid. Both modes of interaction are very sensitive to the quaternary structure of hemoglobin. To directly view the interaction of NO with quaternary-T deoxyhemoglobin, crystallographic studies were carried out on crystals of deoxyhemoglobin that were exposed to gaseous NO under a variety of conditions. Consistent with previous spectroscopic studies in solution, these crystallographic studies show that the binding of NO to the heme groups of crystalline wild-type deoxyhemoglobin ruptures the Fe-proximal histidine bonds of the alpha-subunits but not the beta-subunits. This finding supports Perutz's theory that ligand binding induces tension in the alpha Fe-proximal histidine bond. To test Perutz's theory, deoxy crystals of the mutant hemoglobin betaW37E were exposed to NO. This experiment was carried out because previous studies have shown that this mutation greatly reduces the quaternary constraints that oppose the ligand-induced movement of the alpha-heme Fe atom into the plane of the porphyrin ring. As hypothesized, the Fe-proximal histidine bonds in both the beta- and the alpha-subunits remain intact in crystalline betaW37E after exposure to NO. With regard to S-nitrosocysteine or cysteine oxide formation, no evidence for the reaction of NO with any cysteine residues was detected under anaerobic conditions. However, when deoxyhemoglobin crystals are first exposed to air and then to NO, the appearance of additional electron density indicates that Cys93(F9)beta has been modified, most likely to cysteinesulfenic acid. This modification of Cys93(F9)beta disrupts the intrasubunit salt bridge between His146(HC3)beta and Asp94(FG1)beta, a key feature of the quaternary-T hemoglobin structure. Also presented is a reanalysis of our previous crystallographic studies [Chan, N.-L., et al. (1998) Biochemistry 37, 16459-16464] of the interaction of NO with liganded hemoglobin in the quaternary-R2 structure. These studies showed additional electron density at Cys93(F9)beta that was consistent with an NO adduct. However, for reasons discussed in this paper, we now believe that this adduct may be the Hb-S-N.-O-H radical intermediate and not Hb-S-N=O as previously suggested.


  • Organizational Affiliation

    Department of Biochemistry, College of Medicine, The University of Iowa, Iowa City, IA 52242, USA.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Hemoglobin alpha chain
A, C
141Homo sapiensMutation(s): 0 
UniProt & NIH Common Fund Data Resources
Find proteins for P69905 (Homo sapiens)
Explore P69905 
Go to UniProtKB:  P69905
PHAROS:  P69905
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP69905
Sequence Annotations
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
Hemoglobin beta chain
B, D
146Homo sapiensMutation(s): 1 
UniProt & NIH Common Fund Data Resources
Find proteins for P68871 (Homo sapiens)
Explore P68871 
Go to UniProtKB:  P68871
PHAROS:  P68871
GTEx:  ENSG00000244734 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP68871
Sequence Annotations
Expand
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.11 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.201 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 97.2α = 90
b = 100.4β = 90
c = 66.2γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
SDMSdata reduction
SDMSdata scaling
X-PLORphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-12-23
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2023-08-23
    Changes: Data collection, Database references, Derived calculations, Refinement description
  • Version 1.4: 2023-11-15
    Changes: Data collection
  • Version 1.5: 2024-10-16
    Changes: Structure summary