28MB | pdb_000028mb

Structure of Human Aldehyde oxidase under TCEP-reducing conditions

• PDB DOI: https://doi.org/10.2210/pdb28MB/pdb

• Classification: OXIDOREDUCTASE
• Organism(s): Homo sapiens
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 2026-02-06 Released: 2026-07-29 
• Deposition Author(s): Videira, C., Esmaeeli, M., Leimkuhler, S., Romao, M.J., Mota, C.
• Funding Organization(s): Fundacao para a Ciencia e a Tecnologia

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.31 Å
• R-Value Free: 
  0.241 (Depositor), 0.241 (DCC) 
• R-Value Work: 
  0.209 (Depositor), 0.210 (DCC) 

Starting Model: experimental

Literature

Structure of human aldehyde oxidase under tris(2-carboxyethyl)phosphine reducing conditions.

Videira, C., Esmaeeli, M., Leimkuhler, S., Romao, M.J., Mota, C.

(2026) Acta Crystallogr F Struct Biol Commun 82: 275-282

• PubMed: 42504845 
• DOI: https://doi.org/10.1107/S2053230X26006904
• Primary Citation Related Structures: 
  28MB


• PubMed Abstract: 
  

  The importance of human aldehyde oxidase (hAOX1) has increased in recent decades due to its involvement in drug metabolism. Inhibition studies involving hAOX1 are extensive and a common reducing agent, dithiothreitol (DTT), was recently found to inactivate the enzyme. However, in previous crystallographic studies of hAOX1, DTT was found to be essential for crystallization. To surpass this concern, another reducing agent was used in crystallization trials. Using tris(2-carboxyethyl)phosphine (TCEP), a sulfur-free reducing agent, it was possible to obtain well ordered crystals of wild-type hAOX1 and a variant, hAOX1_6A, which diffracted beyond 2.3 Å resolution. Instead of the typical star-shaped crystals of hAOX1, at pH 4.7 plates are obtained in the orthorhombic space group P2 ₁ 2 ₁ 2 with two molecules in the asymmetric unit. Activity assays with the enzyme incubated with both reducing agents show that in contrast to DTT, TCEP did not inactivate hAOX1. The replacement of DTT with TCEP in the crystallization of hAOX1 provides a strategy to circumvent enzyme inactivation during crystallographic studies, allowing future applications of new assays, such as time-resolved crystallography.

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Organizational Affiliation: 
• UCIBIO, Applied Molecular Biosciences Unit and Associate Laboratory i4HB - Institute for Health and Bioeconomy, Department of Chemistry NOVA School of Science and Technology, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany.

Biological Assembly 1  

Global Symmetry: Cyclic - C2  (Explore in 3D)
Global Stoichiometry: Homo 2-mer - A2 

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

Biological Assembly Evidence: gel filtration

Macromolecule Content 

• Total Structure Weight: 299.7 kDa 
• Atom Count: 20,291 
• Modeled Residue Count: 2,583 
• Deposited Residue Count: 2,676 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Aldehyde oxidase	A, B	1,338	Homo sapiens	Mutation(s): 6  Gene Names: AOX1, AO EC: 1.2.3.1 (PDB Primary Data), 1.17.3 (PDB Primary Data)
UniProt & NIH Common Fund Data Resources
Find proteins for Q06278 (Homo sapiens) Explore Q06278  Go to UniProtKB:  Q06278
PHAROS:  Q06278 GTEx:  ENSG00000138356

Small Molecules

Ligands 6 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
FAD (Subject of Investigation/LOI)	E [auth A], M [auth B]	FLAVIN-ADENINE DINUCLEOTIDE C27 H33 N9 O15 P2 VWWQXMAJTJZDQX-UYBVJOGSSA-N
MTE (Subject of Investigation/LOI)	I [auth A], P [auth B]	PHOSPHONIC ACIDMONO-(2-AMINO-5,6-DIMERCAPTO-4-OXO-3,7,8A,9,10,10A-HEXAHYDRO-4H-8-OXA-1,3,9,10-TETRAAZA-ANTHRACEN-7-YLMETHYL)ESTER C10 H14 N5 O6 P S2 HPEUEJRPDGMIMY-IFQPEPLCSA-N
FES (Subject of Investigation/LOI)	C [auth A], D [auth A], K [auth B], L [auth B]	FE2/S2 (INORGANIC) CLUSTER Fe2 S2 NIXDOXVAJZFRNF-UHFFFAOYSA-N
MOS (Subject of Investigation/LOI)	J [auth A], Q [auth B]	DIOXOTHIOMOLYBDENUM(VI) ION H Mo O2 S BDSRWPHSAKXXRG-UHFFFAOYSA-M
MLI	F [auth A], G [auth A], H [auth A], O [auth B]	MALONATE ION C3 H2 O4 OFOBLEOULBTSOW-UHFFFAOYSA-L
GOL	N [auth B]	GLYCEROL C3 H8 O3 PEDCQBHIVMGVHV-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.31 Å
• R-Value Free:  0.241 (Depositor), 0.241 (DCC) 
• R-Value Work:  0.209 (Depositor), 0.210 (DCC) 

Diffraction Data: https://doi.org/10.15151/ESRF-ES-2019876801

Space Group: P 2₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 191.204	α = 90
b = 273.118	β = 90
c = 77.883	γ = 90

Software Package:

Software Name	Purpose
REFMAC	refinement
PHASER	phasing
autoPROC	data processing
STARANISO	data scaling
XDS	data reduction
Aimless	data scaling
XSCALE	data scaling
pointless	data scaling

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-07-29 
Deposition Author(s): Videira, C., Esmaeeli, M., Leimkuhler, S., Romao, M.J., Mota, C.

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Funding Organization	Location	Grant Number
Fundacao para a Ciencia e a Tecnologia	Portugal	2023.18077.ICDT
Fundacao para a Ciencia e a Tecnologia	Portugal	UIDP/04378/2020
Fundacao para a Ciencia e a Tecnologia	Portugal	UIDB/04378/2020
Fundacao para a Ciencia e a Tecnologia	Portugal	LA/P/0140/2020

Revision History  

• Version 1.0: 2026-07-29
  Type: Initial release
  
• Version 1.1: 2026-08-05
  Changes: Database references
• Version 1.2: 2026-08-12
  Type: Remediation
  Reason: Metalloprotein remediation
  Changes: Derived calculations, Structure summary
• Version 1.3: 2026-08-19
  Changes: Database references