The structure and function of a novel two-site calcium-binding fragment of calmodulin

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the least restraint violations,structures with the lowest energy 

wwPDB Validation   3D Report Full Report

This is version 1.4 of the entry. See complete history


Calcium-induced folding of a fragment of calmodulin composed of EF-hands 2 and 3

Lakowski, T.M.Lee, G.M.Okon, M.Reid, R.E.McIntosh, L.P.

(2007) Protein Sci 16: 1119-1132

  • DOI: https://doi.org/10.1110/ps.072777107
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Calmodulin (CaM) is an EF-hand protein composed of two calcium (Ca(2+))-binding EF-hand motifs in its N-domain (EF-1 and EF-2) and two in its C-domain (EF-3 and EF-4). In this study, we examined the structure, dynamics, and Ca(2+)-binding properties of a fragment of CaM containing only EF-2 and EF-3 and the intervening linker sequence (CaM2/3). Based on NMR spectroscopic analyses, Ca(2+)-free CaM2/3 is predominantly unfolded, but upon binding Ca(2+), adopts a monomeric structure composed of two EF-hand motifs bridged by a short antiparallel beta-sheet. Despite having an "even-odd" pairing of EF-hands, the tertiary structure of CaM2/3 is similar to both the "odd-even" paired N- and C-domains of Ca(2+)-ligated CaM, with the conformationally flexible linker sequence adopting the role of an inter-EF-hand loop. However, unlike either CaM domain, CaM2/3 exhibits stepwise Ca(2+) binding with a K (d1) = 30 +/- 5 microM to EF-3, and a K (d2) > 1000 microM to EF-2. Binding of the first equivalent of Ca(2+) induces the cooperative folding of CaM2/3. In the case of native CaM, stacking interactions between four conserved aromatic residues help to hold the first and fourth helices of each EF-hand domain together, while the loop between EF-hands covalently tethers the second and third helices. In contrast, these aromatic residues lie along the second and third helices of CaM2/3, and thus are positioned adjacent to the loop between its "even-odd" paired EF-hands. This nonnative hydrophobic core packing may contribute to the weak Ca(2+) affinity exhibited by EF-2 in the context of CaM2/3.

  • Organizational Affiliation

    Faculty of Pharmaceutical Sciences, Division of Biomolecular and Pharmaceutical Chemistry, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Calmodulin68Homo sapiensMutation(s): 0 
Gene Names: 

UniProt & NIH Common Fund Data Resources
Find proteins for P0DP23 (Homo sapiens)
Explore P0DP23 
Go to UniProtKB:  P0DP23
GTEx:  ENSG00000198668 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0DP23
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CA

Download Ideal Coordinates CCD File 
B [auth A],
C [auth A]
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the least restraint violations,structures with the lowest energy 

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-05-01
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2022-03-09
    Changes: Data collection, Database references, Derived calculations
  • Version 1.4: 2024-05-29
    Changes: Data collection