2.05A resolution structure of the CS-b5R domains of human Ncb5or (NADP+ form)

Experimental Data Snapshot

  • Resolution: 2.05 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.174 
  • R-Value Observed: 0.177 

wwPDB Validation   3D Report Full Report

Currently 6MV2 does not have a validation slider image.

This is version 1.3 of the entry. See complete history


Crystal structures of the naturally fused CS and cytochrome b5reductase (b5R) domains of Ncb5or reveal an expanded CS fold, extensive CS-b5R interactions and productive binding of the NAD(P)+nicotinamide ring.

Benson, D.R.Lovell, S.Mehzabeen, N.Galeva, N.Cooper, A.Gao, P.Battaile, K.P.Zhu, H.

(2019) Acta Crystallogr D Struct Biol 75: 628-638

  • DOI: https://doi.org/10.1107/S205979831900754X
  • Primary Citation of Related Structures:  
    6MV1, 6MV2

  • PubMed Abstract: 

    Ncb5or (NADH-cytochrome b 5 oxidoreductase), a cytosolic ferric reductase implicated in diabetes and neurological diseases, comprises three distinct domains, cytochrome b 5 (b 5 ) and cytochrome b 5 reductase (b 5 R) domains separated by a CHORD-Sgt1 (CS) domain, and a novel 50-residue N-terminal region. Understanding how interdomain interactions in Ncb5or facilitate the shuttling of electrons from NAD(P)H to heme, and how the process compares with the microsomal b 5 (Cyb5A) and b 5 R (Cyb5R3) system, is of interest. A high-resolution structure of the b 5 domain (PDB entry 3lf5) has previously been reported, which exhibits substantial differences in comparison to Cyb5A. The structural characterization of a construct comprising the naturally fused CS and b 5 R domains with bound FAD and NAD + (PDB entry 6mv1) or NADP + (PDB entry 6mv2) is now reported. The structures reveal that the linker between the CS and b 5 R cores is more ordered than predicted, with much of it extending the β-sandwich motif of the CS domain. This limits the flexibility between the two domains, which recognize one another via a short β-sheet motif and a network of conserved side-chain hydrogen bonds, salt bridges and cation-π interactions. Notable differences in FAD-protein interactions in Ncb5or and Cyb5R3 provide insight into the selectivity for docking of their respective b 5 redox partners. The structures also afford a structural explanation for the unusual ability of Ncb5or to utilize both NADH and NADPH, and represent the first examples of native, fully oxidized b 5 R family members in which the nicotinamide ring of NAD(P) + resides in the active site. Finally, the structures, together with sequence alignments, show that the b 5 R domain is more closely related to single-domain Cyb5R proteins from plants, fungi and some protists than to Cyb5R3 from animals.

  • Organizational Affiliation

    Protein Production Group, The University of Kansas, 2034 Becker Drive, Lawrence, KS 66047, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cytochrome b5 reductase 4367Homo sapiensMutation(s): 0 
Gene Names: CYB5R4NCB5OR
UniProt & NIH Common Fund Data Resources
Find proteins for Q7L1T6 (Homo sapiens)
Explore Q7L1T6 
Go to UniProtKB:  Q7L1T6
GTEx:  ENSG00000065615 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ7L1T6
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on FAD

Download Ideal Coordinates CCD File 
C27 H33 N9 O15 P2
Query on NAP

Download Ideal Coordinates CCD File 
C21 H28 N7 O17 P3
Experimental Data & Validation

Experimental Data

  • Resolution: 2.05 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.174 
  • R-Value Observed: 0.177 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 56.265α = 90
b = 68.842β = 97.43
c = 57.63γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling
PDB_EXTRACTdata extraction

Structure Validation

View Full Validation Report

Currently 6MV2 does not have a validation slider image.

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesP30GM110761

Revision History  (Full details and data files)

  • Version 1.0: 2019-07-17
    Type: Initial release
  • Version 1.1: 2019-07-24
    Changes: Data collection, Database references
  • Version 1.2: 2020-01-01
    Changes: Author supporting evidence
  • Version 1.3: 2023-10-11
    Changes: Data collection, Database references, Refinement description