Crystal structure of aldehyde dehydrogenase 21 (ALDH21) from Physcomitrella patens in its apoform

Experimental Data Snapshot

  • Resolution: 2.15 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.184 
  • R-Value Observed: 0.186 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


The ALDH21 gene found in lower plants and some vascular plants codes for a NADP(+) -dependent succinic semialdehyde dehydrogenase.

Kopecna, M.Vigouroux, A.Vilim, J.Koncitikova, R.Briozzo, P.Hajkova, E.Jaskova, L.von Schwartzenberg, K.Sebela, M.Morera, S.Kopecny, D.

(2017) Plant J 92: 229-243

  • DOI: https://doi.org/10.1111/tpj.13648
  • Primary Citation of Related Structures:  
    5MZ5, 5MZ8, 5N5S

  • PubMed Abstract: 

    Lower plant species including some green algae, non-vascular plants (bryophytes) as well as the oldest vascular plants (lycopods) and ferns (monilophytes) possess a unique aldehyde dehydrogenase (ALDH) gene named ALDH21, which is upregulated during dehydration. However, the gene is absent in flowering plants. Here, we show that ALDH21 from the moss Physcomitrella patens codes for a tetrameric NADP + -dependent succinic semialdehyde dehydrogenase (SSALDH), which converts succinic semialdehyde, an intermediate of the γ-aminobutyric acid (GABA) shunt pathway, into succinate in the cytosol. NAD + is a very poor coenzyme for ALDH21 unlike for mitochondrial SSALDHs (ALDH5), which are the closest related ALDH members. Structural comparison between the apoform and the coenzyme complex reveal that NADP + binding induces a conformational change of the loop carrying Arg-228, which seals the NADP + in the coenzyme cavity via its 2'-phosphate and α-phosphate groups. The crystal structure with the bound product succinate shows that its carboxylate group establishes salt bridges with both Arg-121 and Arg-457, and a hydrogen bond with Tyr-296. While both arginine residues are pre-formed for substrate/product binding, Tyr-296 moves by more than 1 Å. Both R121A and R457A variants are almost inactive, demonstrating a key role of each arginine in catalysis. Our study implies that bryophytes but presumably also some green algae, lycopods and ferns, which carry both ALDH21 and ALDH5 genes, can oxidize SSAL to succinate in both cytosol and mitochondria, indicating a more diverse GABA shunt pathway compared with higher plants carrying only the mitochondrial ALDH5.

  • Organizational Affiliation

    Institute for Integrative Biology of the Cell (I2BC), CNRS-CEA-Univ. Paris-Sud, Université Paris-Saclay, Avenue de la Terrasse, F-91198, Gif-sur-Yvette, France.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D
515Physcomitrium patensMutation(s): 0 
Gene Names: PHYPADRAFT_215149
Find proteins for A9SS48 (Physcomitrium patens)
Explore A9SS48 
Go to UniProtKB:  A9SS48
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA9SS48
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on PEG

Download Ideal Coordinates CCD File 
J [auth A],
S [auth B]
C4 H10 O3
Query on GOL

Download Ideal Coordinates CCD File 
AA [auth D]
BA [auth D]
E [auth A]
F [auth A]
G [auth A]
AA [auth D],
BA [auth D],
E [auth A],
F [auth A],
G [auth A],
L [auth B],
M [auth B],
N [auth B],
T [auth C],
U [auth C],
V [auth C],
Z [auth D]
C3 H8 O3
Query on EDO

Download Ideal Coordinates CCD File 
CA [auth D]
H [auth A]
I [auth A]
K [auth A]
O [auth B]
CA [auth D],
H [auth A],
I [auth A],
K [auth A],
O [auth B],
P [auth B],
Q [auth B],
R [auth B],
W [auth C],
X [auth C],
Y [auth C]
C2 H6 O2
Experimental Data & Validation

Experimental Data

  • Resolution: 2.15 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.184 
  • R-Value Observed: 0.186 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 91.802α = 90
b = 151.793β = 90
c = 158.518γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
GACRCzech Republic15-22322S

Revision History  (Full details and data files)

  • Version 1.0: 2017-08-09
    Type: Initial release
  • Version 1.1: 2017-10-18
    Changes: Database references
  • Version 1.2: 2024-01-17
    Changes: Data collection, Database references, Refinement description