6LPI

Crystal Structure of AHAS holo-enzyme

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.85 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.167 
  • R-Value Observed: 0.170 

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Literature

Molecular architecture of the acetohydroxyacid synthase holoenzyme.

Zhang, Y., Li, Y., Liu, X., Sun, J., Li, X., Lin, J., Yang, X., Xi, Z., Shen, Y.

(2020) Biochem J 477: 2439-2449

  • DOI: 10.1042/BCJ20200292
  • Primary Citation of Related Structures:  
    6LPI

  • PubMed Abstract: 

    • The acetohydroxyacid synthase (AHAS) holoenzyme catalyzes the first step of branch-chain amino acid biosynthesis and is essential for plants and bacteria. It consists of a regulatory subunit (RSU) and a catalytic subunit (CSU). The allosteric mechanism of the AHAS holoenzyme has remained elusive for decades ...

    The acetohydroxyacid synthase (AHAS) holoenzyme catalyzes the first step of branch-chain amino acid biosynthesis and is essential for plants and bacteria. It consists of a regulatory subunit (RSU) and a catalytic subunit (CSU). The allosteric mechanism of the AHAS holoenzyme has remained elusive for decades. Here, we determined the crystal structure of the AHAS holoenzyme, revealing the association between the RSU and CSU in an A2B2 mode. Structural analysis in combination with mutational studies demonstrated that the RSU dimer forms extensive interactions with the CSU dimer, in which a conserved salt bridge between R32 and D120 may act as a trigger to open the activation loop of the CSU, resulting in the activation of the CSU by the RSU. Our study reveals the activation mechanism of the AHAS holoenzyme.

    Organizational Affiliation: 

    Collaborative Innovation Center of Chemical Science and Engineering, Weijin 94, Tianjin 300071, China.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Acetolactate synthase isozyme 1 small subunitA [auth E],
C [auth F],
E [auth G],
G [auth H]		127Escherichia coli K-12Mutation(s): 0 
Gene Names: ilvN, b3670, JW3645
EC: 2.2.1.6
UniProt
Find proteins for P0ADF8 (Escherichia coli (strain K12))
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Go to UniProtKB:  P0ADF8
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UniProt GroupP0ADF8
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Acetolactate synthase isozyme 1 large subunitB [auth A],
D [auth B],
F [auth C],
H [auth D]		562Escherichia coli K-12Mutation(s): 0 
Gene Names: ilvB, b3671, JW3646
EC: 2.2.1.6
UniProt
Find proteins for P08142 (Escherichia coli (strain K12))
Explore P08142 
Go to UniProtKB:  P08142
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP08142
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.85 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.167 
  • R-Value Observed: 0.170 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 111.173α = 90
b = 104.577β = 105.68
c = 118.535γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
PDB_EXTRACTdata extraction
HKL-2000data reduction
HKL-2000data scaling
PHASERphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2020-11-18
    Type: Initial release