Crystal structure of non-symbiotic plant hemoglobin from rice, B10 mutant F40L

Experimental Data Snapshot

  • Resolution: 2.30 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.203 

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Role of Phenylalanine B10 in Plant Nonsymbiotic Hemoglobins

Smagghe, B.J.Kundu, S.Hoy, J.A.Halder, P.Weiland, T.R.Savage, A.Venugopal, A.Goodman, M.Premer, S.Hargrove, M.S.

(2006) Biochemistry 45: 9735-9745

  • DOI: https://doi.org/10.1021/bi060716s
  • Primary Citation of Related Structures:  
    2GNV, 2GNW

  • PubMed Abstract: 

    All plants contain an unusual class of hemoglobins that display bis-histidyl coordination yet are able to bind exogenous ligands such as oxygen. Structurally homologous hexacoordinate hemoglobins (hxHbs) are also found in animals (neuroglobin and cytoglobin) and some cyanobacteria, where they are thought to play a role in free radical scavenging or ligand sensing. The plant hxHbs can be distinguished from the others because they are only weakly hexcacoordinate in the ferrous state, yet no structural mechanism for regulating hexacoordination has been articulated to account for this behavior. Plant hxHbs contain a conserved Phe at position B10 (Phe(B10)), which is near the reversibly coordinated distal His(E7). We have investigated the effects of Phe(B10) mutation on kinetic and equilibrium constants for hexacoordination and exogenous ligand binding in the ferrous and ferric oxidation states. Kinetic and equilibrium constants for hexacoordination and ligand binding along with CO-FTIR spectroscopy, midpoint reduction potentials, and the crystal structures of two key mutant proteins (F40W and F40L) reveal that Phe(B10) is an important regulatory element in hexacoordination. We show that Phe at this position is the only amino acid that facilitates stable oxygen binding to the ferrous Hb and the only one that promotes ligand binding in the ferric oxidation states. This work presents a structural mechanism for regulating reversible intramolecular coordination in plant hxHbs.

  • Organizational Affiliation

    Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Non-symbiotic hemoglobin 1
A, B
165Oryza sativaMutation(s): 1 
Gene Names: HB1GLB1A
Find proteins for O04986 (Oryza sativa subsp. japonica)
Explore O04986 
Go to UniProtKB:  O04986
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO04986
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.30 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.203 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 125.286α = 90
b = 125.286β = 90
c = 56.25γ = 120
Software Package:
Software NamePurpose
d*TREKdata scaling
PDB_EXTRACTdata extraction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

  • Released Date: 2006-04-25 
  • Deposition Author(s): Hoy, J.A.

Revision History  (Full details and data files)

  • Version 1.0: 2006-04-25
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-18
    Changes: Refinement description
  • Version 1.4: 2021-10-20
    Changes: Database references, Derived calculations
  • Version 1.5: 2023-08-30
    Changes: Data collection, Refinement description