5E2J

Crystal structure of single mutant thermostable endoglucanase (D468A) from Alicyclobacillus acidocaldarius


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.205 

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This is version 1.1 of the entry. See complete history


Literature

Polarity Alteration of a Calcium Site Induces a Hydrophobic Interaction Network and Enhances Cel9A Endoglucanase Thermostability.

Wang, H.J.Hsiao, Y.Y.Chen, Y.P.Ma, T.Y.Tseng, C.P.

(2016) Appl Environ Microbiol 82: 1662-1674

  • DOI: 10.1128/AEM.03326-15
  • Primary Citation of Related Structures:  
    5E2J

  • PubMed Abstract: 
  • Structural calcium sites control protein thermostability and activity by stabilizing native folds and changing local conformations. Alicyclobacillus acidocaldarius survives in thermal-acidic conditions and produces an endoglucanase Cel9A (AaCel9A) which contains a calcium-binding site (Ser465 to Val470) near the catalytic cleft ...

    Structural calcium sites control protein thermostability and activity by stabilizing native folds and changing local conformations. Alicyclobacillus acidocaldarius survives in thermal-acidic conditions and produces an endoglucanase Cel9A (AaCel9A) which contains a calcium-binding site (Ser465 to Val470) near the catalytic cleft. By superimposing the Ca(2+)-free and Ca(2+)-bounded conformations of the calcium site, we found that Ca(2+) induces hydrophobic interactions between the calcium site and its nearby region by driving a conformational change. The hydrophobic interactions at the high-B-factor region could be enhanced further by replacing the surrounding polar residues with hydrophobic residues to affect enzyme thermostability and activity. Therefore, the calcium-binding residue Asp468 (whose side chain directly ligates Ca(2+)), Asp469, and Asp471 of AaCel9A were separately replaced by alanine and valine. Mutants D468A and D468V showed increased activity compared with those of the wild type with 0 mM or 10 mM Ca(2+) added, whereas the Asp469 or Asp471 substitution resulted in decreased activity. The D468A crystal structure revealed that mutation D468A triggered a conformational change similar to that induced by Ca(2+) in the wild type and developed a hydrophobic interaction network between the calcium site and the neighboring hydrophobic region (Ala113 to Ala117). Mutations D468V and D468A increased 4.5°C and 5.9°C, respectively, in melting temperature, and enzyme half-life at 75°C increased approximately 13 times. Structural comparisons between AaCel9A and other endoglucanases of the GH9 family suggested that the stability of the regions corresponding to the AaCel9A calcium site plays an important role in GH9 endoglucanase catalysis at high temperature.


    Organizational Affiliation

    Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
EndoglucanaseA, B570Alicyclobacillus acidocaldarius subsp. acidocaldariusMutation(s): 1 
Gene Names: celA
EC: 3.2.1.4
UniProt
Find proteins for Q9AJS0 (Alicyclobacillus acidocaldarius subsp. acidocaldarius)
Explore Q9AJS0 
Go to UniProtKB:  Q9AJS0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9AJS0
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.205 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 55.421α = 90
b = 144.374β = 90
c = 158.704γ = 90
Software Package:
Software NamePurpose
BALBESphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2016-02-03
    Type: Initial release
  • Version 1.1: 2016-04-20
    Changes: Database references