3I3D

E. COLI (lacZ) BETA-GALACTOSIDASE (M542A) IN COMPLEX WITH IPTG


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.2 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.185 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Role of Met-542 as a guide for the conformational changes of Phe-601 that occur during the reaction of β-galactosidase (Escherichia coli).

Dugdale, M.L.Dymianiw, D.L.Minhas, B.K.D'Angelo, I.Huber, R.E.

(2010) Biochem.Cell Biol. 88: 861-869

  • DOI: 10.1139/O10-009
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The Met-542 residue of β-galactosidase is important for the enzyme's activity because it acts as a guide for the movement of the benzyl side chain of Phe-601 between two stable positions. This movement occurs in concert with an important conformation ...

    The Met-542 residue of β-galactosidase is important for the enzyme's activity because it acts as a guide for the movement of the benzyl side chain of Phe-601 between two stable positions. This movement occurs in concert with an important conformational change (open vs. closed) of an active site loop (residues 794-803). Phe-601 and Arg-599, which interact with each other via the π electrons of Phe-601 and the guanidium cation of Arg-599, move out of their normal positions and become disordered when Met-542 is replaced by an Ala residue because of the loss of the guide. Since the backbone carbonyl of Phe-601 is a ligand for Na(+), the Na(+) also moves out of its normal position and becomes disordered; the Na(+) binds about 120 times more poorly. In turn, two other Na(+) ligands, Asn-604 and Asp-201, become disordered. A substrate analog (IPTG) restored Arg-599, Phe-601, and Na(+) to their normal open-loop positions, whereas a transition state analog d-galactonolactone) restored them to their normal closed-loop positions. These compounds also restored order to Phe-601, Asn-604, Asp-201, and Na(+). Binding energy was, however, necessary to restore structure and order. The K(s) values of oNPG and pNPG and the competitive K(i) values of substrate analogs were 90-250 times higher than with native enzyme, whereas the competitive K(i) values of transition state analogs were ~3.5-10 times higher. Because of this, the E•S energy level is raised more than the E•transition state energy level and less activation energy is needed for galactosylation. The galactosylation rates (k₂) of M542A-β-galactosidase therefore increase. However, the rate of degalactosylation (k₃) decreased because the E•transition state complex is less stable.


    Organizational Affiliation

    Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-galactosidase
A, B, C, D
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 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NA
Query on NA

Download SDF File 
Download CCD File 
A, B, C, D
SODIUM ION
Na
FKNQFGJONOIPTF-UHFFFAOYSA-N
 Ligand Interaction
MG
Query on MG

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Download CCD File 
A, B, C, D
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
DMS
Query on DMS

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Download CCD File 
A, B, C, D
DIMETHYL SULFOXIDE
C2 H6 O S
IAZDPXIOMUYVGZ-UHFFFAOYSA-N
 Ligand Interaction
IPT
Query on IPT

Download SDF File 
Download CCD File 
A, B, C, D
ISOPROPYL-1-BETA-D-THIOGALACTOSIDE
1-(ISOPROPYLTHIO)-BETA-GALACTOPYRANSIDE
C9 H18 O5 S
BPHPUYQFMNQIOC-NXRLNHOXSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
IPTKi: 76000 nM (99) BINDINGDB
IPTKi: 10300000 nM BINDINGMOAD
IPTKi: 10300000 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.2 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.185 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 151.540α = 90.00
b = 162.390β = 90.00
c = 203.730γ = 90.00
Software Package:
Software NamePurpose
ADSCdata collection
CNSphasing
CNSrefinement
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2010-05-12
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2011-08-10
    Type: Database references