Pseudoreversion of the Catalytic Activity of Y14F by the Additional Tyrosine-to-Phenylalanine Substitution(s) in the Hydrogen Bond Network of Delta-5-3-Ketosteroid Isomerase from Pheudomonas putida Biotype B

Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.258 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.206 

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Pseudoreversion of the Catalytic Activity of Y14F by the Additional Substitution(S) of Tyrosine with Phenylalanine in the Hydrogen Bond Network of Delta (5)-3-Ketosteroid Isomerase from Pseudomonas Putida Biotype B

Choi, G.Ha, N.-C.Kim, M.-S.Hong, B.-H.Oh, B.-H.Choi, K.Y.

(2001) Biochemistry 40: 6828

  • DOI: https://doi.org/10.1021/bi002767+
  • Primary Citation of Related Structures:  
    1E97, 1EA2

  • PubMed Abstract: 

    Delta5-3-ketosteroid isomerase (KSI) from Pseudomonas putida Biotype B catalyzes the allylic isomerization of Delta5-3-ketosteroids to their conjugated Delta4-isomers via a dienolate intermediate. Two electrophilic catalysts, Tyr-14 and Asp-99, are involved in a hydrogen bond network that comprises Asp-99 Odelta2...O of Wat504...Tyr-14 Oeta...Tyr-55 Oeta.Tyr-30 Oeta in the active site of P. putida KSI. Even though neither Tyr-30 nor Tyr-55 plays an essential role in catalysis by the KSI, the catalytic activity of Y14F could be increased ca. 26-51-fold by the additional Y30F and/or Y55F mutation in the hydrogen bond network. To identify the structural basis for the pseudoreversion in the KSI, crystal structures of Y14F and Y14F/Y30F/Y55F have been determined at 1.8 and 2.0 A resolution, respectively. Comparisons of the two structures near the catalytic center indicate that the hydrogen bond between Asp-99 Odelta2 and C3-O of the steroid, which is perturbed by the Y14F mutation, can be partially restored to that in the wild-type enzyme by the additional Y30F/Y55F mutations. The kinetic parameters of the tyrosine mutants with the additional D99N or D99L mutation also support the idea that Asp-99 contributes to catalysis more efficiently in Y14F/Y30F/Y55F than in Y14F. In contrast to the catalytic mechanism of Y14F, the C4 proton of the steroid substrate was found to be transferred to the C6 position in Y14F/Y30F/Y55F with little exchange of the substrate 4beta-proton with a solvent deuterium based on the reaction rate in D2O. Taken together, our findings strongly suggest that the improvement in the catalytic activity of Y14F by the additional Y30F/Y55F mutations is due to the changes in the structural integrity at the catalytic site and the resulting restoration of the proton-transfer mechanism in Y14F/Y30F/Y55F.

  • Organizational Affiliation

    Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
STEROID DELTA-ISOMERASE131Pseudomonas putidaMutation(s): 1 
Gene Names: ksi
Find proteins for P07445 (Pseudomonas putida)
Explore P07445 
Go to UniProtKB:  P07445
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP07445
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.258 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.206 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 36.13α = 90
b = 95.83β = 90
c = 74.55γ = 90
Software Package:
Software NamePurpose

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-11-01
    Type: Initial release
  • Version 1.1: 2013-06-19
    Changes: Database references, Derived calculations, Non-polymer description, Other, Refinement description, Structure summary, Version format compliance