6KNZ

Crystal structure of T2R-TTL-KXO1 complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.48 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.220 
  • R-Value Observed: 0.221 

wwPDB Validation   3D Report Full Report


Ligand Structure Quality Assessment 


This is version 1.3 of the entry. See complete history


Literature

Reversible binding of the anticancer drug KXO1 (tirbanibulin) to the colchicine-binding site of beta-tubulin explains KXO1's low clinical toxicity.

Niu, L.Yang, J.Yan, W.Yu, Y.Zheng, Y.Ye, H.Chen, Q.Chen, L.

(2019) J Biol Chem 294: 18099-18108

  • DOI: https://doi.org/10.1074/jbc.RA119.010732
  • Primary Citation of Related Structures:  
    6KNZ

  • PubMed Abstract: 

    KXO1 (tirbanibulin or KX2-391) is as a non-ATP-competitive inhibitor of SRC proto-oncogene nonreceptor tyrosine kinase (SRC) and is being clinically investigated for the management of various cancers and actinic keratosis. Recently, KXO1 has also been shown to strongly inhibit tubulin. Interestingly, unlike conventional tubulin-targeting drugs, KXO1 has exhibited low toxicity in preclinical and clinical studies, but the reason for this remains elusive, as are the KXO1-binding site and other details of the interaction of KXO1 with tubulin. Here, cell-based experiments revealed that KXO1 induces tubulin depolymerization and G 2 /M phase cell cycle arrest at low nanomolar concentrations, similar to colchicine, used as a positive control. Results from biochemical experiments, including an N , N -ethylenebis(iodoacetamide) competition assay, disclosed that KXO1 binds to the colchicine-binding site on β-tubulin, further confirmed by the crystal structure of the tubulin-KXO1 complex at 2.5-Å resolution. A high-quality electron density map of the crystallographic data enabled us to unambiguously determine the position and orientation of KXO1 in the colchicine-binding site, revealing the detailed interactions between KXO1 and tubulin. We also found that KXO1 binds reversibly to purified tubulin, induces a totally reversible cellular effect (G 2 /M cell cycle arrest), and possesses no cellular toxicity 5 days after drug washout, explaining KXO1's low toxicity. In summary, we show that KXO1 binds to the colchicine-binding site of tubulin and resolved the crystal structure of the tubulin-KXO1 complex. Importantly, KXO1's reversible binding to tubulin explains its clinically low toxicity, an insight that could guide further clinical applications of KXO1.


  • Organizational Affiliation

    State Key Laboratory of Biotherapy and Cancer Center, West China Hospital of Sichuan University and Collaborative Innovation Center of Biotherapy and Cancer, Chengdu 610041, China.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Tubulin alpha-1B chain
A, C
450Bos taurusMutation(s): 0 
UniProt
Find proteins for P81947 (Bos taurus)
Explore P81947 
Go to UniProtKB:  P81947
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP81947
Sequence Annotations
Expand
  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
Tubulin beta-2B chain
B, D
445Bos taurusMutation(s): 0 
UniProt
Find proteins for Q6B856 (Bos taurus)
Explore Q6B856 
Go to UniProtKB:  Q6B856
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ6B856
Sequence Annotations
Expand
  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 3
MoleculeChains Sequence LengthOrganismDetailsImage
Stathmin-4143Rattus norvegicusMutation(s): 0 
Gene Names: Stmn4
UniProt
Find proteins for P63043 (Rattus norvegicus)
Explore P63043 
Go to UniProtKB:  P63043
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP63043
Sequence Annotations
Expand
  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 4
MoleculeChains Sequence LengthOrganismDetailsImage
Tubulin tyrosine ligase384Gallus gallusMutation(s): 0 
Gene Names: TTL
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
Expand
  • Reference Sequence
Small Molecules
Ligands 7 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
GTP
Query on GTP

Download Ideal Coordinates CCD File 
G [auth A],
Q [auth C],
V [auth D]
GUANOSINE-5'-TRIPHOSPHATE
C10 H16 N5 O14 P3
XKMLYUALXHKNFT-UUOKFMHZSA-N
ACP
Query on ACP

Download Ideal Coordinates CCD File 
Z [auth F]PHOSPHOMETHYLPHOSPHONIC ACID ADENYLATE ESTER
C11 H18 N5 O12 P3
UFZTZBNSLXELAL-IOSLPCCCSA-N
GDP
Query on GDP

Download Ideal Coordinates CCD File 
J [auth B]GUANOSINE-5'-DIPHOSPHATE
C10 H15 N5 O11 P2
QGWNDRXFNXRZMB-UUOKFMHZSA-N
DN0 (Subject of Investigation/LOI)
Query on DN0

Download Ideal Coordinates CCD File 
O [auth B],
W [auth D]
2-[5-[4-(2-morpholin-4-ylethoxy)phenyl]pyridin-2-yl]-~{N}-(phenylmethyl)ethanamide
C26 H29 N3 O3
HUNGUWOZPQBXGX-UHFFFAOYSA-N
MES
Query on MES

Download Ideal Coordinates CCD File 
L [auth B],
P [auth B]
2-(N-MORPHOLINO)-ETHANESULFONIC ACID
C6 H13 N O4 S
SXGZJKUKBWWHRA-UHFFFAOYSA-N
CA
Query on CA

Download Ideal Coordinates CCD File 
I [auth A]
M [auth B]
N [auth B]
S [auth C]
U [auth D]
I [auth A],
M [auth B],
N [auth B],
S [auth C],
U [auth D],
X [auth E]
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
MG
Query on MG

Download Ideal Coordinates CCD File 
H [auth A],
K [auth B],
R [auth C],
T [auth D],
Y [auth F]
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
Binding Affinity Annotations 
IDSourceBinding Affinity
DN0 Binding MOAD:  6KNZ Kd: 1260 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.48 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.220 
  • R-Value Observed: 0.221 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 104.928α = 90
b = 157.059β = 90
c = 182.21γ = 90
Software Package:
Software NamePurpose
HKL-2000data scaling
PHENIXrefinement
PDB_EXTRACTdata extraction
HKL-3000data reduction
HKL-3000phasing

Structure Validation

View Full Validation Report



Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2019-10-23
    Type: Initial release
  • Version 1.1: 2019-10-30
    Changes: Data collection, Database references
  • Version 1.2: 2019-12-18
    Changes: Database references
  • Version 1.3: 2023-11-22
    Changes: Data collection, Database references, Derived calculations, Refinement description