Biological Assembly 1  

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Global Symmetry: Cyclic - C2  (3D View)
Global Stoichiometry: Hetero 4-mer - A2B2 Pseudo Symmetry: Dihedral - D2  (3D View)
Pseudo Stoichiometry: Homo 4-mer -A4 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 64659.09 
• Atom Count: 4564 
• Residue Count: 574 
• Unique protein chains: 2

1BBB

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

• DOI: 10.2210/pdb1BBB/pdb

• Classification: OXYGEN TRANSPORT
• Organism(s): Homo sapiens


• Deposited: 1992-04-29 Released: 1993-10-31 
• Deposition Author(s): Arnone, A., Silva, M.M.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.7 Å

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

• PubMed: 1512262 


• 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 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.

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Organizational Affiliation: 

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

Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details
HEMOGLOBIN A (CARBONMONOXY) (ALPHA CHAIN)	A, C	141	Homo sapiens	Mutation(s): 0  Gene Names: HBA1, HBA2
Find proteins for P69905 (Homo sapiens) Go to Gene View: HBA1 HBA2 Go to UniProtKB:  P69905

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details
HEMOGLOBIN A (CARBONMONOXY) (BETA CHAIN)	B, D	146	Homo sapiens	Mutation(s): 0  Gene Names: HBB
Find proteins for P68871 (Homo sapiens) Go to Gene View: HBB Go to UniProtKB:  P68871

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram & Interactions
HEM	A, B, C, D	PROTOPORPHYRIN IX CONTAINING FE HEME C34 H32 Fe N4 O4 KABFMIBPWCXCRK-RGGAHWMASA-L
CMO	A, B, C, D	CARBON MONOXIDE C O UGFAIRIUMAVXCW-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.7 Å
• Space Group: P 2₁ 2₁ 2₁

Unit Cell:

Length (Å)	Angle (°)
a = 97.500	α = 90.00
b = 101.500	β = 90.00
c = 61.100	γ = 90.00

Software Package:

Software Name	Purpose
PROLSQ	refinement

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 1992-04-29 
• Released Date: 1993-10-31 
• Deposition Author(s): Arnone, A., Silva, M.M.

Revision History 

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