1CIR

COMPLEX OF TWO FRAGMENTS OF CI2 [(1-40)(DOT)(41-64)]


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Submitted: 20 

wwPDB Validation   3D Report Full Report


This is version 1.4 of the entry. See complete history


Literature

Towards the complete structural characterization of a protein folding pathway: the structures of the denatured, transition and native states for the association/folding of two complementary fragments of cleaved chymotrypsin inhibitor 2. Direct evidence for a nucleation-condensation mechanism

Neira, J.L.Davis, B.Ladurner, A.G.Buckle, A.M.Gay Gde, P.Fersht, A.R.

(1996) Structure 1: 189-208

  • DOI: https://doi.org/10.1016/s1359-0278(96)00031-4
  • Primary Citation of Related Structures:  
    1CIQ, 1CIR

  • PubMed Abstract: 

    Single-module proteins, such as chymotrypsin inhibitor 2 (CI2), fold as a single cooperative unit. To solve its folding pathway, we must characterize, under conditions that favour folding, its denatured state, its transition state, and its final folded structure. To obtain a "denatured state' that can readily be thus characterized, we have used a trick of cleaving CI2 into two complementary fragments that associate and fold in a similar way to intact protein. Fragment CI2(1-40)-which contains the sequence of the single alpha-helix, spanning residues 12-24-and CI2(41-64), and mutants thereof, were analyzed by NMR spectroscopy, the transition state for association/folding was characterized by the protein engineering method, and the structure of the complex was solved by NMR and X-ray crystallography. Both isolated fragments are largely disordered. The transition state for association/folding is structured around a nucleus of a nearly fully formed alpha-helix, as is the transition state for the folding of intact CI2, from residues Ser12 to Leu21, Ala16, a residue from the helix whose sidechain is buried in the hydrophobic core, makes interactions with Leu49 and Ile57 in the other fragment. Ala16 makes its full interaction energy in the transition state for the association/folding reaction, just as found during the folding of the intact protein. The specific contacts in the transition state from a nucleus that extends from one fragment to the next, but the nucleus is only "flickeringly' present in the denatured state. This is direct evidence for the nucleation-condensation mechanism in which the nucleus is only weakly formed in the ground state and develops in the transition state. The low conformational preferences in the denatured state are not enough to induce significant local secondary structure, but are reinforced by tertiary interactions during the rapid condensation around the nucleus.


  • Organizational Affiliation

    MRC Unit for Protein Function and Design, Cambridge Centre for Protein Engineering, UK.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CHYMOTRYPSIN INHIBITOR 240Hordeum vulgareMutation(s): 0 
UniProt
Find proteins for P01053 (Hordeum vulgare)
Explore P01053 
Go to UniProtKB:  P01053
Entity Groups  
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UniProt GroupP01053
Sequence Annotations
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  • Reference Sequence

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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
CHYMOTRYPSIN INHIBITOR 224Hordeum vulgareMutation(s): 0 
UniProt
Find proteins for P01053 (Hordeum vulgare)
Explore P01053 
Go to UniProtKB:  P01053
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP01053
Sequence Annotations
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  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
HSE
Query on HSE
A
L-PEPTIDE LINKINGC4 H9 N O3SER
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Submitted: 20 

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1996-01-29
    Type: Initial release
  • Version 1.1: 2008-03-24
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2022-02-16
    Changes: Database references, Derived calculations, Other
  • Version 1.4: 2024-05-22
    Changes: Data collection