3B0M

M175K mutant of assimilatory nitrite reductase (Nii3) from tobbaco leaf


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.197 
  • R-Value Work: 0.163 
  • R-Value Observed: 0.165 

Starting Model: experimental
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This is version 2.0 of the entry. See complete history


Literature

Structure-function relationship of assimilatory nitrite reductases from the leaf and root of tobacco based on high resolution structures

Nakano, S.Takahashi, M.Sakamoto, A.Morikawa, H.Katayanagi, K.

(2012) Protein Sci 21: 383-395

  • DOI: https://doi.org/10.1002/pro.2025
  • Primary Citation of Related Structures:  
    3B0G, 3B0H, 3B0J, 3B0L, 3B0M, 3B0N

  • PubMed Abstract: 

    Tobacco expresses four isomers of assimilatory nitrite reductase (aNiR), leaf-type (Nii1 and Nii3), and root-type (Nii2 and Nii4). The high-resolution crystal structures of Nii3 and Nii4, determined at 1.25 and 2.3 Å resolutions, respectively, revealed that both proteins had very similar structures. The Nii3 structure provided detailed geometries for the [4Fe-4S] cluster and the siroheme prosthetic groups. We have generated two types of Nii3 variants: one set focuses on residue Met175 (Nii3-M175G, Nii3-M175E, and Nii3-M175K), a residue that is located on the substrate entrance pathway; the second set targets residue Gln448 (Nii3-Q448K), a residue near the prosthetic groups. Comparison of the structures and kinetics of the Nii3 wild-type (Nii3-WT) and the Met175 variants showed that the hydrophobic side-chain of Met175 facilitated enzyme efficiency (k(cat) /K(m) ). The Nii4-WT has Lys449 at the equivalent position of Gln448 in Nii3-WT. The enzyme activity assay revealed that the turnover number (k(cat) ) and Michaelis constant (K(m) ) of Nii4-WT were lower than those of Nii3-WT. However, the k(cat) /K(m) of Nii4-WT was about 1.4 times higher than that of Nii3-WT. A comparison of the kinetics of the Nii3-Q448K and Nii4-K449Q variants revealed that the change in k(cat) /K(m) was brought about by the difference in Residue 448 (defined as Gln448 in Nii3 and Lys449 in Nii4). By combining detailed crystal structures with enzyme kinetics, we have proposed that Nii3 is the low-affinity and Nii4 is the high-affinity aNiR.


  • Organizational Affiliation

    Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Nitrite reductase584Nicotiana tabacumMutation(s): 1 
Gene Names: nii3
EC: 1.7.7.1
UniProt
Find proteins for Q76KB0 (Nicotiana tabacum)
Explore Q76KB0 
Go to UniProtKB:  Q76KB0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ76KB0
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.197 
  • R-Value Work: 0.163 
  • R-Value Observed: 0.165 
  • Space Group: P 4 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 133.152α = 90
b = 133.152β = 90
c = 77.586γ = 90
Software Package:
Software NamePurpose
SCALEPACKdata scaling
REFMACrefinement
PDB_EXTRACTdata extraction
ADSCdata collection
HKL-2000data reduction
MOLREPphasing

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-02-22
    Type: Initial release
  • Version 1.1: 2023-11-01
    Changes: Data collection, Database references, Derived calculations, Refinement description
  • Version 2.0: 2023-12-27
    Changes: Data collection, Non-polymer description, Structure summary