Crystal structure of Acat5 thiolase from Ascaris suum in complex with coenzyme A

Experimental Data Snapshot

  • Resolution: 1.60 Å
  • R-Value Free: 0.173 
  • R-Value Work: 0.146 
  • R-Value Observed: 0.147 

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Structural and Biochemical Studies of Substrate Selectivity in Ascaris suum Thiolases.

Blaisse, M.R.Fu, B.Chang, M.C.Y.

(2018) Biochemistry 57: 3155-3166

  • DOI: https://doi.org/10.1021/acs.biochem.7b01123
  • Primary Citation of Related Structures:  
    6BJ9, 6BJA, 6BJB

  • PubMed Abstract: 

    Thiolases are a class of carbon-carbon bond forming enzymes with important applications in biotechnology and metabolic engineering as they provide a general method for the condensation of two acyl coenzyme A (CoA) substrates. As such, developing a greater understanding of their substrate selectivity would expand our ability to engineer the enzymatic or microbial production of a broad range of small-molecule targets. Here, we report the crystal structures and biochemical characterization of Acat2 and Acat5, two biosynthetic thiolases from Ascaris suum with varying selectivity toward branched compared to linear compounds. The structure of the Acat2-C91S mutant bound to propionyl-CoA shows that the terminal methyl group of the substrate, representing the α-branch point, is directed toward the conserved Phe 288 and Met 158 residues. In Acat5, the Phe ring is rotated to accommodate a hydroxyl-π interaction with an adjacent Thr side chain, decreasing space in the binding pocket and possibly accounting for its strong preference for linear substrates compared to Acat2. Comparison of the different Acat thiolase structures shows that Met 158 is flexible, adopting alternate conformations with the side chain rotated toward or away from a covering loop at the back of the active site. Mutagenesis of residues in the covering loop in Acat5 with the corresponding residues from Acat2 allows for highly increased accommodation of branched substrates, whereas the converse mutations do not significantly affect Acat2 substrate selectivity. Our results suggest an important contribution of second-shell residues to thiolase substrate selectivity and offer insights into engineering this enzyme class.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Acetyl-CoA acetyltransferase A397Ascaris suumMutation(s): 0 
Find proteins for F1L3N8 (Ascaris suum)
Explore F1L3N8 
Go to UniProtKB:  F1L3N8
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupF1L3N8
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on CSO
Experimental Data & Validation

Experimental Data

  • Resolution: 1.60 Å
  • R-Value Free: 0.173 
  • R-Value Work: 0.146 
  • R-Value Observed: 0.147 
  • Space Group: I 2 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 71.6615α = 90
b = 111.78β = 90
c = 112.756γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling
PHENIXmodel building

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Science Foundation (NSF, United States)United StatesCHE-1413862

Revision History  (Full details and data files)

  • Version 1.0: 2018-02-07
    Type: Initial release
  • Version 1.1: 2018-06-20
    Changes: Data collection, Database references
  • Version 1.2: 2019-11-27
    Changes: Author supporting evidence
  • Version 1.3: 2023-10-04
    Changes: Data collection, Database references, Refinement description
  • Version 1.4: 2023-11-15
    Changes: Data collection