Duplication-extension of Helix A of T4 lysozyme

Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.208 
  • R-Value Observed: 0.214 

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This is version 1.6 of the entry. See complete history


Relocation or duplication of the helix A sequence of T4 lysozyme causes only modest changes in structure but can increase or decrease the rate of folding.

Sagermann, M.Baase, W.A.Mooers, B.H.Gay, L.Matthews, B.W.

(2004) Biochemistry 43: 1296-1301

  • DOI: https://doi.org/10.1021/bi035702q
  • Primary Citation of Related Structures:  
    1P56, 1P5C

  • PubMed Abstract: 

    In T4 lysozyme, helix A is located at the amino terminus of the sequence but is associated with the C-terminal domain in the folded structure. To investigate the implications of this arrangement for the folding of the protein, we first created a circularly permuted variant with a new amino terminus at residue 12. In effect, this moves the sequence corresponding to helix A from the N- to the C-terminus of the molecule. The protein crystallized nonisomorphously with the wild type but has a very similar structure, showing that the unit consisting of helix A and the C-terminal domain can be reconstituted from a contiguous polypeptide chain. The protein is less stable than the wild type but folds slightly faster. We then produced a second variant in which the helix A sequence was appended at the C-terminus (as in the first variant), but was also restored at the N-terminus (as in the wild type). This variant has two helix A sequences, one at the N-terminus and the other at the C-terminus, each of which can compete for the same site in the folded protein. The crystal structure shows that it is the N-terminal sequence that folds in a manner similar to that of the wild type, whereas the copy at the C-terminus is forced to loop out. The stability of this protein is much closer to that of the wild type, but its rate of folding is significantly slower. The reduction in rate is attributed to the presence of the two identical sequence segments which compete for a single, mutually exclusive, site.

  • Organizational Affiliation

    Institute of Molecular Biology, Howard Hughes Medical Institute, and Department of Physics, 1229, University of Oregon, Eugene, Oregon 97403-1229, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
PROTEIN (Lysozyme)176Tequatrovirus T4Mutation(s): 2 
Gene Names: Gene product E
Find proteins for P00720 (Enterobacteria phage T4)
Explore P00720 
Go to UniProtKB:  P00720
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP00720
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.208 
  • R-Value Observed: 0.214 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 60.3α = 90
b = 60.3β = 90
c = 96.396γ = 120
Software Package:
Software NamePurpose
SCALEPACKdata scaling
MOSFLMdata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-05-04
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2019-07-24
    Changes: Data collection, Refinement description
  • Version 1.4: 2019-08-14
    Changes: Data collection
  • Version 1.5: 2021-10-27
    Changes: Database references
  • Version 1.6: 2023-08-16
    Changes: Data collection, Refinement description