Structure of maize cytokinin oxidase/dehydrogenase 2 (ZmCKO2)

Experimental Data Snapshot

  • Resolution: 2.04 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.193 
  • R-Value Observed: 0.194 

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Kinetic and structural investigation of the cytokinin oxidase/dehydrogenase active site.

Kopecny, D.Koncitikova, R.Popelka, H.Briozzo, P.Vigouroux, A.Kopecna, M.Zalabak, D.Sebela, M.Skopalova, J.Frebort, I.Morera, S.

(2016) FEBS J 283: 361-377

  • DOI: https://doi.org/10.1111/febs.13581
  • Primary Citation of Related Structures:  
    3S1C, 3S1D, 3S1E, 3S1F, 4ML8, 4MLA, 4O95, 4OAL

  • PubMed Abstract: 

    Cytokinins are hormones that regulate plant development and their environmental responses. Their levels are mainly controlled by the cytokinin oxidase/dehydrogenase (CKO), which oxidatively cleaves cytokinins using redox-active electron acceptors. CKO belongs to the group of flavoproteins with an 8α-N1-histidyl FAD covalent linkage. Here, we investigated the role of seven active site residues, H105, D169, E288, V378, E381, P427 and L492, in substrate binding and catalysis of the CKO1 from maize (Zea mays, ZmCKO1) combining site-directed mutagenesis with kinetics and X-ray crystallography. We identify E381 as a key residue for enzyme specificity that restricts substrate binding as well as quinone electron acceptor binding. We show that D169 is important for catalysis and that H105 covalently linked to FAD maintains the enzyme's structural integrity, stability and high rates with electron acceptors. The L492A mutation significantly modulates the cleavage of aromatic cytokinins and zeatin isomers. The high resolution X-ray structures of ZmCKO1 and the E381S variant in complex with N6-(2-isopentenyl)adenosine reveal the binding mode of cytokinin ribosides. Those of ZmCKO2 and ZmCKO4a contain a mobile domain, which might contribute to binding of the N9 substituted cytokinins.

  • Organizational Affiliation

    Department of Protein Biochemistry and Proteomics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Olomouc, Czech Republic.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cytokinin oxidase 2
A, B
501Zea maysMutation(s): 0 
Gene Names: cko2
Find proteins for Q709Q5 (Zea mays)
Explore Q709Q5 
Go to UniProtKB:  Q709Q5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ709Q5
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 4 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on FAD

Download Ideal Coordinates CCD File 
BA [auth B],
C [auth A]
C27 H33 N9 O15 P2
Query on GOL

Download Ideal Coordinates CCD File 
CA [auth B],
K [auth A],
OA [auth B]
C3 H8 O3
Query on EDO

Download Ideal Coordinates CCD File 
EA [auth B]
G [auth A]
I [auth A]
J [auth A]
W [auth A]
EA [auth B],
G [auth A],
I [auth A],
J [auth A],
W [auth A],
Y [auth A]
C2 H6 O2
Query on IPA

Download Ideal Coordinates CCD File 
AA [auth B]
D [auth A]
DA [auth B]
E [auth A]
F [auth A]
AA [auth B],
D [auth A],
DA [auth B],
E [auth A],
F [auth A],
FA [auth B],
GA [auth B],
H [auth A],
HA [auth B],
IA [auth B],
JA [auth B],
KA [auth B],
L [auth A],
LA [auth B],
M [auth A],
MA [auth B],
N [auth A],
NA [auth B],
O [auth A],
P [auth A],
PA [auth B],
Q [auth A],
R [auth A],
S [auth A],
T [auth A],
U [auth A],
V [auth A],
X [auth A],
Z [auth A]
C3 H8 O
Experimental Data & Validation

Experimental Data

  • Resolution: 2.04 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.193 
  • R-Value Observed: 0.194 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 75.72α = 90
b = 181.89β = 90
c = 196.96γ = 90
Software Package:
Software NamePurpose
DNAdata collection
XDSdata reduction
XDSdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-03-11
    Type: Initial release
  • Version 1.1: 2015-11-04
    Changes: Database references
  • Version 1.2: 2016-03-23
    Changes: Database references