1IJH

CHOLESTEROL OXIDASE FROM STREPTOMYCES ASN485LEU MUTANT


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.53 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.163 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

The presence of a hydrogen bond between asparagine 485 and the pi system of FAD modulates the redox potential in the reaction catalyzed by cholesterol oxidase.

Yin, Y.Sampson, N.S.Vrielink, A.Lario, P.I.

(2001) Biochemistry 40: 13779-13787


  • PubMed Abstract: 
  • Cholesterol oxidase catalyzes the oxidation and isomerization of cholesterol to cholest-4-en-3-one. An asparagine residue (Asn485) at the active site is believed to play an important role in catalysis. To test the precise role of Asn485, we mutated i ...

    Cholesterol oxidase catalyzes the oxidation and isomerization of cholesterol to cholest-4-en-3-one. An asparagine residue (Asn485) at the active site is believed to play an important role in catalysis. To test the precise role of Asn485, we mutated it to a leucine and carried out kinetic and crystallographic studies. Steady-state kinetic analysis revealed a 1300-fold decrease in the oxidation k(cat)/K(m) for the mutant enzyme whereas the k(cat)/K(m) for isomerization is only 60-fold slower. The primary kinetic isotope effect in the mutant-catalyzed reaction indicates that 3alpha-H transfer remains the rate-determining step. Measurement of the reduction potentials for the wild-type and N485L enzymes reveals a 76 mV decrease in the reduction potential of the FAD for the mutant enzyme relative to wild type. The crystal structure of the mutant, determined to 1.5 A resolution, reveals a repositioning of the side chain of Met122 near Leu485 to form a hydrophobic pocket. Furthermore, the movement of Met122 facilitates the binding of an additional water molecule, possibly mimicking the position of the equatorial hydroxyl group of the steroid substrate. The wild-type enzyme shows a novel N-H...pi interaction between the side chain of Asn485 and the pyrimidine ring of the cofactor. The loss of this interaction in the N485L mutant destabilizes the reduced flavin and accounts for the decreased reduction potential and rate of oxidation. Thus, the observed structural rearrangement of residues at the active site, as well as the kinetic data and thermodynamic data for the mutant, suggests that Asn485 is important for creating an electrostatic potential around the FAD cofactor enhancing the oxidation reaction.


    Organizational Affiliation

    Department of Molecular, Sinsheimer Laboratory, University of California, Santa Cruz, Santa Cruz, California 95064, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
CHOLESTEROL OXIDASE
A
504Streptomyces sp. (strain SA-COO)Mutation(s): 1 
Gene Names: choA
EC: 1.1.3.6
Find proteins for P12676 (Streptomyces sp. (strain SA-COO))
Go to UniProtKB:  P12676
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
FAD
Query on FAD

Download SDF File 
Download CCD File 
A
FLAVIN-ADENINE DINUCLEOTIDE
C27 H33 N9 O15 P2
VWWQXMAJTJZDQX-UYBVJOGSSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.53 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.163 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 51.261α = 90.00
b = 72.881β = 105.11
c = 63.034γ = 90.00
Software Package:
Software NamePurpose
SHELXphasing
SHELXL-97refinement
DENZOdata reduction
SCALEPACKdata scaling
SHELXmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-12-28
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance