Crystal structure of the kinase domain of CIPK24/SOS2

Experimental Data Snapshot

  • Resolution: 3.30 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.271 
  • R-Value Observed: 0.271 

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Structural Basis of the Regulatory Mechanism of the Plant Cipk Family of Protein Kinases Controlling Ion Homeostasis and Abiotic Stress

Chaves-Sanjuan, A.Sanchez-Barrena, M.J.Gonzalez-Rubio, J.M.Moreno, M.Ragel, P.Jimenez, M.Pardo, J.M.Martinez-Ripoll, M.Quintero, F.J.Albert, A.

(2014) Proc Natl Acad Sci U S A 111: E4532

  • DOI: https://doi.org/10.1073/pnas.1407610111
  • Primary Citation of Related Structures:  
    4CZT, 4CZU, 4D28

  • PubMed Abstract: 

    Plant cells have developed specific protective molecular machinery against environmental stresses. The family of CBL-interacting protein kinases (CIPK) and their interacting activators, the calcium sensors calcineurin B-like (CBLs), work together to decode calcium signals elicited by stress situations. The molecular basis of biological activation of CIPKs relies on the calcium-dependent interaction of a self-inhibitory NAF motif with a particular CBL, the phosphorylation of the activation loop by upstream kinases, and the subsequent phosphorylation of the CBL by the CIPK. We present the crystal structures of the NAF-truncated and pseudophosphorylated kinase domains of CIPK23 and CIPK24/SOS2. In addition, we provide biochemical data showing that although CIPK23 is intrinsically inactive and requires an external stimulation, CIPK24/SOS2 displays basal activity. This data correlates well with the observed conformation of the respective activation loops: Although the loop of CIPK23 is folded into a well-ordered structure that blocks the active site access to substrates, the loop of CIPK24/SOS2 protrudes out of the active site and allows catalysis. These structures together with biochemical and biophysical data show that CIPK kinase activity necessarily requires the coordinated releases of the activation loop from the active site and of the NAF motif from the nucleotide-binding site. Taken all together, we postulate the basis for a conserved calcium-dependent NAF-mediated regulation of CIPKs and a variable regulation by upstream kinases.

  • Organizational Affiliation

    Departamento de Cristalografía y Biología Estructural, Instituto de Química Física "Rocasolano," Consejo Superior de Investigaciones Científicas, Madrid E-28006, Spain; and.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D
446Arabidopsis thalianaMutation(s): 7 
Find proteins for Q9LDI3 (Arabidopsis thaliana)
Explore Q9LDI3 
Go to UniProtKB:  Q9LDI3
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9LDI3
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.30 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.271 
  • R-Value Observed: 0.271 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 69.111α = 104.85
b = 71.353β = 100.32
c = 77.834γ = 118.96
Software Package:
Software NamePurpose
XDSdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2014-10-15
    Type: Initial release
  • Version 1.1: 2014-11-05
    Changes: Database references
  • Version 1.2: 2014-12-17
    Changes: Data collection
  • Version 1.3: 2017-12-06
    Changes: Data collection, Structure summary
  • Version 1.4: 2023-12-20
    Changes: Data collection, Database references, Other, Refinement description