3MUY

E. coli (lacZ) beta-galactosidase (R599A)


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.5 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.179 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Importance of Arg-599 of beta-galactosidase (Escherichia coli) as an anchor for the open conformations of Phe-601 and the active-site loop

Dugdale, M.L.Vance, M.L.Wheatley, R.W.Driedger, M.R.Nibber, A.Tran, A.Huber, R.E.

(2010) Biochem.Cell Biol. 88: 969-979

  • DOI: 10.1139/O10-144

  • PubMed Abstract: 
  • Structural and kinetic data show that Arg-599 of β-galactosidase plays an important role in anchoring the "open" conformations of both Phe-601 and an active-site loop (residues 794-803). When alanine was substituted for Arg-599, the conformations of ...

    Structural and kinetic data show that Arg-599 of β-galactosidase plays an important role in anchoring the "open" conformations of both Phe-601 and an active-site loop (residues 794-803). When alanine was substituted for Arg-599, the conformations of Phe-601 and the loop shifted towards the "closed" positions because interactions with the guanidinium side chain were lost. Also, Phe-601, the loop, and Na+, which is ligated by the backbone carbonyl of Phe-601, lost structural order, as indicated by large B-factors. IPTG, a substrate analog, restored the conformations of Phe-601 and the loop of R599A-β-galactosidase to the open state found with IPTG-complexed native enzyme and partially reinstated order. ᴅ-Galactonolactone, a transition state analog, restored the closed conformations of R599A-β-galactosidase to those found with ᴅ-galactonolactone-complexed native enzyme and completely re-established the order. Substrates and substrate analogs bound R599A-β-galactosidase with less affinity because the closed conformation does not allow substrate binding and extra energy is required for Phe-601 and the loop to open. In contrast, transition state analog binding, which occurs best when the loop is closed, was several-fold better. The higher energy level of the enzyme•substrate complex and the lower energy level of the first transition state means that less activation energy is needed to form the first transition state and thus the rate of the first catalytic step (k2) increased substantially. The rate of the second catalytic step (k3) decreased, likely because the covalent form is more stabilized than the second transition state when Phe-601 and the loop are closed. The importance of the guanidinium group of Arg-599 was confirmed by restoration of conformation, order, and activity by guanidinium ions.


    Organizational Affiliation

    Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-D-galactosidase
1, 2, 3, 4
1023Escherichia coli (strain K12)Mutation(s): 1 
Gene Names: lacZ
EC: 3.2.1.23
Find proteins for P00722 (Escherichia coli (strain K12))
Go to UniProtKB:  P00722
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NA
Query on NA

Download SDF File 
Download CCD File 
1, 2, 3, 4
SODIUM ION
Na
FKNQFGJONOIPTF-UHFFFAOYSA-N
 Ligand Interaction
MG
Query on MG

Download SDF File 
Download CCD File 
1, 2, 3, 4
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
DMS
Query on DMS

Download SDF File 
Download CCD File 
1, 2, 3, 4
DIMETHYL SULFOXIDE
C2 H6 O S
IAZDPXIOMUYVGZ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.5 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.179 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 149.266α = 90.00
b = 167.237β = 90.00
c = 200.614γ = 90.00
Software Package:
Software NamePurpose
SCALAdata scaling
CNSphasing
ADSCdata collection
MOSFLMdata reduction
CNSrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-03-16
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2012-08-22
    Type: Database references