1O23

CRYSTAL STRUCTURE OF LACTOSE SYNTHASE IN THE PRESENCE OF UDP-GLUCOSE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.32 Å
  • R-Value Free: 0.265 
  • R-Value Work: 0.201 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Alpha-Lactalbumin (La) Stimulates Milk Beta-1,4-Galactosyltransferase I (Beta 4Gal-T1) to Transfer Glucose from Udp-Glucose to N-Acetylglucosamine. Crystal Structure of Beta 4Gal-T1 X La Complex with Udp-Glc.

Ramakrishnan, B.Shah, P.S.Qasba, P.K.

(2001) J.Biol.Chem. 276: 37665-37671

  • DOI: 10.1074/jbc.M102458200
  • Primary Citation of Related Structures:  1JN8, 1JNA, 1JNC, 1NMM, 1NWG

  • PubMed Abstract: 
  • beta-1,4-Galactosyltransferase 1 (Gal-T1) transfers galactose (Gal) from UDP-Gal to N-acetylglucosamine (GlcNAc), which constitutes its normal galactosyltransferase (Gal-T) activity. In the presence of alpha-lactalbumin (LA), it transfers Gal to Glc, ...

    beta-1,4-Galactosyltransferase 1 (Gal-T1) transfers galactose (Gal) from UDP-Gal to N-acetylglucosamine (GlcNAc), which constitutes its normal galactosyltransferase (Gal-T) activity. In the presence of alpha-lactalbumin (LA), it transfers Gal to Glc, which is its lactose synthase (LS) activity. It also transfers glucose (Glc) from UDP-Glc to GlcNAc, constituting the glucosyltransferase (Glc-T) activity, albeit at an efficiency of only 0.3-0.4% of Gal-T activity. In the present study, we show that LA increases this activity almost 30-fold. It also enhances the Glc-T activity toward various N-acyl substituted glucosamine acceptors. Steady state kinetic studies of Glc-T reaction show that the K(m) for the donor and acceptor substrates are high in the absence of LA. In the presence of LA, the K(m) for the acceptor substrate is reduced 30-fold, whereas for UDP-Glc it is reduced only 5-fold. In order to understand this property, we have determined the crystal structures of the Gal-T1.LA complex with UDP-Glc x Mn(2+) and with N-butanoyl-glucosamine (N-butanoyl-GlcN), a preferred sugar acceptor in the Glc-T activity. The crystal structures reveal that although the binding of UDP-Glc is quite similar to UDP-Gal, there are few significant differences observed in the hydrogen bonding interactions between UDP-Glc and Gal-T1. Based on the present kinetic and crystal structural studies, a possible explanation for the role of LA in the Glc-T activity has been proposed.


    Organizational Affiliation

    Structural Glycobiology Section, Laboratory of Experimental and Computational Biology, Center for Cancer Research, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
ALPHA-LACTALBUMIN
A, C
123Mus musculusGene Names: Lalba
Find proteins for P29752 (Mus musculus)
Go to UniProtKB:  P29752
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
BETA-1,4-GALACTOSYLTRANSFERASE
B, D
286Bos taurusGene Names: B4GALT1 (GALT, GGTB2)
EC: 2.4.1.22, 2.4.1.38, 2.4.1.90, 2.4.1.-
Find proteins for P08037 (Bos taurus)
Go to Gene View: B4GALT1
Go to UniProtKB:  P08037
Small Molecules
Ligands 6 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MN
Query on MN

Download SDF File 
Download CCD File 
B, D
MANGANESE (II) ION
Mn
WAEMQWOKJMHJLA-UHFFFAOYSA-N
 Ligand Interaction
UPG
Query on UPG

Download SDF File 
Download CCD File 
B, D
URIDINE-5'-DIPHOSPHATE-GLUCOSE
URIDINE-5'-MONOPHOSPHATE GLUCOPYRANOSYL-MONOPHOSPHATE ESTER
C15 H24 N2 O17 P2
HSCJRCZFDFQWRP-JZMIEXBBSA-N
 Ligand Interaction
CA
Query on CA

Download SDF File 
Download CCD File 
A, C
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
PG4
Query on PG4

Download SDF File 
Download CCD File 
A, C
TETRAETHYLENE GLYCOL
C8 H18 O5
UWHCKJMYHZGTIT-UHFFFAOYSA-N
 Ligand Interaction
UDP
Query on UDP

Download SDF File 
Download CCD File 
B, D
URIDINE-5'-DIPHOSPHATE
C9 H14 N2 O12 P2
XCCTYIAWTASOJW-XVFCMESISA-N
 Ligand Interaction
MES
Query on MES

Download SDF File 
Download CCD File 
A
2-(N-MORPHOLINO)-ETHANESULFONIC ACID
C6 H13 N O4 S
SXGZJKUKBWWHRA-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.32 Å
  • R-Value Free: 0.265 
  • R-Value Work: 0.201 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 55.545α = 90.00
b = 99.379β = 104.09
c = 102.568γ = 90.00
Software Package:
Software NamePurpose
DENZOdata reduction
AMoREphasing
SCALEPACKdata scaling
CNSrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-02-25
    Type: Initial release
  • Version 1.1: 2008-04-26
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2013-05-08
    Type: Non-polymer description