Crystal structure of human cytosolic NADP(+)-dependent isocitrate dehydrogenase in complex NADP

Experimental Data Snapshot

  • Resolution: 2.70 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.210 

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Structures of human cytosolic NADP-dependent isocitrate dehydrogenase reveal a novel self-regulatory mechanism of activity

Xu, X.Zhao, J.Xu, Z.Peng, B.Huang, Q.Arnold, E.Ding, J.

(2004) J Biol Chem 279: 33946-33957

  • DOI: https://doi.org/10.1074/jbc.M404298200
  • Primary Citation of Related Structures:  
    1T09, 1T0L

  • PubMed Abstract: 

    Isocitrate dehydrogenases (IDHs) catalyze the oxidative decarboxylation of isocitrate to alpha-ketoglutarate, and regulation of the enzymatic activity of IDHs is crucial for their biological functions. Bacterial IDHs are reversibly regulated by phosphorylation of a strictly conserved serine residue at the active site. Eukaryotic NADP-dependent IDHs (NADP-IDHs) have been shown to have diverse important biological functions; however, their regulatory mechanism remains unclear. Structural studies of human cytosolic NADP-IDH (HcIDH) in complex with NADP and in complex with NADP, isocitrate, and Ca2+ reveal three biologically relevant conformational states of the enzyme that differ substantially in the structure of the active site and in the overall structure. A structural segment at the active site that forms a conserved alpha-helix in all known NADP-IDH structures assumes a loop conformation in the open, inactive form of HcIDH; a partially unraveled alpha-helix in the semi-open, intermediate form; and an alpha-helix in the closed, active form. The side chain of Asp279 of this segment occupies the isocitrate-binding site and forms hydrogen bonds with Ser94 (the equivalent of the phosphorylation site in bacterial IDHs) in the inactive form and chelates the metal ion in the active form. The structural data led us to propose a novel self-regulatory mechanism for HcIDH that mimics the phosphorylation mechanism used by the bacterial homologs, consistent with biochemical and biological data. This mechanism might be applicable to other eukaryotic NADP-IDHs. The results also provide insights into the recognition and specificity of substrate and cofactor by eukaryotic NADP-IDHs.

  • Organizational Affiliation

    Key Laboratory of Proteomics, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.

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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Isocitrate dehydrogenase [NADP] cytoplasmic
A, B
414Homo sapiensMutation(s): 0 
Gene Names: IDH
UniProt & NIH Common Fund Data Resources
Find proteins for O75874 (Homo sapiens)
Explore O75874 
Go to UniProtKB:  O75874
PHAROS:  O75874
GTEx:  ENSG00000138413 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO75874
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on NAP

Download Ideal Coordinates CCD File 
C [auth A],
D [auth B]
C21 H28 N7 O17 P3
Experimental Data & Validation

Experimental Data

  • Resolution: 2.70 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.210 
  • Space Group: P 43 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 82.71α = 90
b = 82.71β = 90
c = 308.03γ = 90
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-06-15
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2023-10-25
    Changes: Data collection, Database references, Derived calculations, Refinement description