1BBB

A THIRD QUATERNARY STRUCTURE OF HUMAN HEMOGLOBIN A AT 1.7-ANGSTROMS RESOLUTION


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.184 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

A third quaternary structure of human hemoglobin A at 1.7-A resolution.

Silva, M.M.Rogers, P.H.Arnone, A.

(1992) J Biol Chem 267: 17248-17256

  • Primary Citation of Related Structures:  
    1BBB

  • PubMed Abstract: 
  • Previous crystallographic studies have shown that human hemoglobin A can adopt two stable quaternary structures, one for deoxyhemoglobin (the T-state) and one for liganded hemoglobin (the R-state). In this paper we report our finding of a second quat ...

    Previous crystallographic studies have shown that human hemoglobin A can adopt two stable quaternary structures, one for deoxyhemoglobin (the T-state) and one for liganded hemoglobin (the R-state). In this paper we report our finding of a second quaternary structure (the R2-state) for liganded hemoglobin A. The magnitudes of the spatial differences between the R- and R2-states are as large as those between the R- and T-states. Of particular interest are the structural changes that occur as a result of R-T and R-R2 transitions at the so-called "switch" region of the critical alpha 1 beta 2 interface. In the R-state, His-97 beta 2 is positioned between Thr-38 alpha 1 and Thr-41 alpha 1, whereas in transition to the T-state His 97 beta 2 must "jump" a turn in the alpha 1 C helix to form nonpolar contacts with Thr-41 alpha 1 and Pro-44 alpha 1. This facet of the R-T transition presents a major steric barrier to the quaternary structure change. In the R2-state, His-97 beta 2 simply rotates away from threonines 38 alpha 1 and 41 alpha 1, breaking contact with these residues and allowing water access to the center of the alpha 1 beta 2 interface. With the switch region in an open position in the R2-state, His-97 beta 2 should be able to move by Thr-41 alpha 1 and make the transition to the T-state with a steric barrier that is less than that for the R-T transition. Thus the R2-state may function as a stable intermediate along a R-R2-T pathway. The T-, R-, and R2-states must coexist in solution. That is, the fact that these states can be crystallized implies that they are all energetically accessible structures. What remains to be determined are the T-to-R, T-to-R2, and R-to-R2 equilibrium constants for hemoglobin under various solution conditions and ligation states. Although this may prove to be difficult, we discuss previously published results which indicate that low concentrations of inorganic anions or low pH may favor the R2-state and at least one alpha 1 beta 2 interface mutation stabilizes a quaternary structure that is very similar to the R2-state.


    Organizational Affiliation

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



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
HEMOGLOBIN A (CARBONMONOXY) (ALPHA CHAIN)AC141Homo sapiensMutation(s): 0 
Gene Names: HBA1HBA2
Find proteins for P69905 (Homo sapiens)
Explore P69905 
Go to UniProtKB:  P69905
NIH Common Fund Data Resources
PHAROS  P69905
Protein Feature View
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
HEMOGLOBIN A (CARBONMONOXY) (BETA CHAIN)BD146Homo sapiensMutation(s): 0 
Gene Names: HBB
Find proteins for P68871 (Homo sapiens)
Explore P68871 
Go to UniProtKB:  P68871
NIH Common Fund Data Resources
PHAROS  P68871
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
HEM
Query on HEM

Download CCD File 
A, B, C, D
PROTOPORPHYRIN IX CONTAINING FE
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
 Ligand Interaction
CMO
Query on CMO

Download CCD File 
A, B, C, D
CARBON MONOXIDE
C O
UGFAIRIUMAVXCW-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.184 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 97.5α = 90
b = 101.5β = 90
c = 61.1γ = 90
Software Package:
Software NamePurpose
PROLSQrefinement

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1993-10-31
    Type: Initial release
  • Version 1.1: 2008-03-28
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance