2K0D

NMR structure of a mutant colicin e7 immunity protein im7 with an extended helix III


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 30 
  • Selection Criteria: target function 

wwPDB Validation   3D Report Full Report


This is version 1.3 of the entry. See complete history


Literature

Amino acid insertion reveals a necessary three-helical intermediate in the folding pathway of the colicin E7 immunity protein Im7.

Knowling, S.E.Figueiredo, A.M.Whittaker, S.B.Moore, G.R.Radford, S.E.

(2009) J Mol Biol 392: 1074-1086

  • DOI: https://doi.org/10.1016/j.jmb.2009.07.085
  • Primary Citation of Related Structures:  
    2K0D

  • PubMed Abstract: 

    The small (87-residue) alpha-helical protein Im7 (an inhibitor protein for colicin E7 that provides immunity to cells producing colicin E7) folds via a three-state mechanism involving an on-pathway intermediate. This kinetic intermediate contains three of four native helices that are oriented in a non-native manner so as to minimise exposed hydrophobic surface area at this point in folding. The short (6-residue) helix III has been shown to be unstructured in the intermediate ensemble and does not dock onto the developing hydrophobic core until after the rate-limiting transition state has been traversed. After helix III has docked, it adopts an alpha-helical secondary structure, and the side chains of residues within this region provide contacts that are crucial to native-state stability. In order to probe further the role of helix III in the folding mechanism of Im7, we created a variant that contains an eight-amino-acid polyalanine-like helix stabilised by a Glu-Arg salt bridge and an Asn-Pro-Gly capping motif, juxtaposed C-terminal to the natural 6-residue helix III. The effect of this insertion on the structure of the native protein and its folding mechanism were studied using NMR and varphi-value analysis, respectively. The results reveal a robust native structure that is not perturbed by the presence of the extended helix III. Mutational analysis performed to probe the folding mechanism of the redesigned protein revealed a conserved mechanism involving the canonical three-helical intermediate. The results suggest that folding via a three-helical species stabilised by both native and non-native interactions is an essential feature of Im7 folding, independent of the helical propensity of helix III.


  • Organizational Affiliation

    Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Colicin-E7 immunity proteinA [auth X]101Escherichia coliMutation(s): 0 
Gene Names: immceiE7
UniProt
Find proteins for Q03708 (Escherichia coli)
Explore Q03708 
Go to UniProtKB:  Q03708
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ03708
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 30 
  • Selection Criteria: target function 

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-01-20
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2022-03-16
    Changes: Data collection, Database references, Derived calculations
  • Version 1.3: 2024-05-29
    Changes: Data collection