1L68

TOLERANCE OF T4 LYSOZYME TO MULTIPLE XAA (RIGHT ARROW) ALA SUBSTITUTIONS: A POLYALANINE ALPHA-HELIX CONTAINING TEN CONSECUTIVE ALANINES


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.165 

wwPDB Validation   3D Report Full Report


This is version 1.4 of the entry. See complete history


Literature

Folding and function of a T4 lysozyme containing 10 consecutive alanines illustrate the redundancy of information in an amino acid sequence.

Heinz, D.W.Baase, W.A.Matthews, B.W.

(1992) Proc Natl Acad Sci U S A 89: 3751-3755

  • DOI: https://doi.org/10.1073/pnas.89.9.3751
  • Primary Citation of Related Structures:  
    1L64, 1L65, 1L66, 1L67, 1L68

  • PubMed Abstract: 

    Single and multiple Xaa----Ala substitutions were constructed in the alpha-helix comprising residues 39-50 in bacteriophage T4 lysozyme. The variant with alanines at 10 consecutive positions (A40-49) folds normally and has activity essentially the same as wild type, although it is less stable. The crystal structure of this polyalanine mutant displays no significant change in the main-chain atoms of the helix when compared with the wild-type structure. The individual substitutions of the solvent-exposed residues Asn-40, Ser-44, and Glu-45 with alanine tend to increase the thermostability of the protein, whereas replacements of the buried or partially buried residues Lys-43 and Leu-46 are destabilizing. The melting temperature of the lysozyme in which Lys-43 and Leu-46 are retained and positions 40, 44, 45, 47, and 48 are substituted with alanine (i.e., A40-42/44-45/47-49) is increased by 3.1 degrees C relative to wild type at pH 3.0, but reduced by 1.6 degrees C at pH 6.7. In the case of the charged amino acids Glu-45 and Lys-48, the changes in melting temperature indicate that the putative salt bridge between these two residues contributes essentially nothing to the stability of the protein. The results clearly demonstrate that there is considerable redundancy in the sequence information in the polypeptide chain; not every amino acid is essential for folding. Also, further evidence is provided that the replacement of fully solvent-exposed residues within alpha-helices with alanines may be a general way to increase protein stability. The general approach may permit a simplification of the protein folding problem by retaining only amino acids proven to be essential for folding and replacing the remainder with alanine.


  • Organizational Affiliation

    Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene 97403.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
LYSOZYME164Tequatrovirus T4Mutation(s): 0 
EC: 3.2.1.17
UniProt
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
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.165 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 60.72α = 90
b = 60.72β = 90
c = 97γ = 120
Software Package:
Software NamePurpose
TNTrefinement

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1991-10-15
    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: 2017-11-29
    Changes: Derived calculations, Other
  • Version 1.4: 2024-02-14
    Changes: Data collection, Database references, Derived calculations