1CBM

THE 1.8 ANGSTROM STRUCTURE OF CARBONMONOXY-BETA4 HEMOGLOBIN: ANALYSIS OF A HOMOTETRAMER WITH THE R QUATERNARY STRUCTURE OF LIGANDED ALPHA2BETA2 HEMOGLOBIN


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.74 Å
  • R-Value Observed: 0.177 

wwPDB Validation   3D Report Full Report


This is version 2.2 of the entry. See complete history


Literature

The 1.8 A structure of carbonmonoxy-beta 4 hemoglobin. Analysis of a homotetramer with the R quaternary structure of liganded alpha 2 beta 2 hemoglobin.

Borgstahl, G.E.Rogers, P.H.Arnone, A.

(1994) J Mol Biol 236: 817-830

  • DOI: https://doi.org/10.1006/jmbi.1994.1191
  • Primary Citation of Related Structures:  
    1CBM

  • PubMed Abstract: 

    The beta-chains isolated from the human hemoglobin alpha 2 beta 2 heterotetramer self-assemble to form a beta 4 homotetramer. We report the structure of the carbonmonoxy-beta 4 (CO beta 4) tetramer refined at a resolution of 1.8 A. Compared to the three known quaternary structures of human hemoglobin, the T state, the R state and the R2 state, the quaternary structure of CO beta 4 most closely resembles the R state. While the degree of structural similarity between CO beta 4 and the R state of liganded alpha 2 beta 2 is quite high, differences between the alpha and beta-chain sequences result in interesting alternative packing arrangements at the subunit interfaces of CO beta 4. In particular, Arg40 beta and Asp99 beta interact across the CO beta 4 equivalent of the alpha 1 beta 2 interface to form two symmetry-related salt bridges that have no counterpart in either liganded or deoxyhemoglobin. Because these salt bridges are near a 2-fold symmetry axis, steric constraints prevent their simultaneous formation, and electron density images of Arg40 beta and Asp99 beta show equally populated dual conformations for the side-chains of both residues. Relative to the liganded alpha 2 beta 2 tetramer, the Arg40 beta...Asp99 beta salt bridges introduce ionic interactions that should strengthen the CO beta 4 tetramer. The CO beta 4 equivalent of the alpha 1 alpha 2 and beta 1 beta 2 interfaces strengthens the tetramer relative to the liganded alpha 2 beta 2 tetramer by tethering both ends of the central cavity. (The entrance to the central cavity is altered so that the N termini move closer together and the C termini further apart, forming an anion binding pocket that is absent in liganded alpha 2 beta 2 hemoglobin.) In contrast, analysis of the CO beta 4 counterpart of the alpha 1 beta 1 interface indicates that this interface is weakened in the CO beta 4 tetramer. These differences in interface stability provide a structural explanation for the published observation that the alpha 2 beta 2 tetramer assembles via a stable alpha 1 beta 1 dimer intermediate, whereas assembly of the CO beta 4 tetramer is characterized more accurately by a monomer-tetramer equilibrium.


  • Organizational Affiliation

    Department of Biochemistry, University of Iowa, Iowa City 52242.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
HEMOGLOBIN BETA 4 (CARBONMONOXY)
A, B, C, D
146Homo sapiensMutation(s): 0 
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
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
HEM
Query on HEM

Download Ideal Coordinates CCD File 
F [auth A],
I [auth B],
L [auth C],
O [auth D]
PROTOPORPHYRIN IX CONTAINING FE
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
SO4
Query on SO4

Download Ideal Coordinates CCD File 
E [auth A],
H [auth B],
K [auth C],
N [auth D]
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
CMO
Query on CMO

Download Ideal Coordinates CCD File 
G [auth A],
J [auth B],
M [auth C],
P [auth D]
CARBON MONOXIDE
C O
UGFAIRIUMAVXCW-UHFFFAOYSA-N
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.74 Å
  • R-Value Observed: 0.177 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 63.3α = 90
b = 82.4β = 90.1
c = 53.7γ = 90
Software Package:
Software NamePurpose
PROLSQrefinement
TNTrefinement

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1994-07-31
    Type: Initial release
  • Version 1.1: 2008-03-24
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 2.0: 2023-02-08
    Type: Remediation
    Changes: Atomic model, Data collection, Database references, Derived calculations, Other
  • Version 2.1: 2023-03-15
    Changes: Advisory
  • Version 2.2: 2024-05-22
    Changes: Data collection