1OQM

A 1:1 complex between alpha-lactalbumin and beta1,4-galactosyltransferase in the presence of UDP-N-acetyl-galactosamine


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Free: 0.244 
  • R-Value Work: 0.194 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structure-based design of beta 1,4-galactosyltransferase I (beta 4Gal-T1) with equally efficient N-acetylgalactosaminyltransferase activity: point mutation broadens beta 4Gal-T1 donor specificity.

Ramakrishnan, B.Qasba, P.K.

(2002) J.Biol.Chem. 277: 20833-20839

  • DOI: 10.1074/jbc.M111183200

  • PubMed Abstract: 
  • beta1,4-Galactosyltransferase I (Gal-T1) normally transfers Gal from UDP-Gal to GlcNAc in the presence of Mn(2+) ion. In the presence of alpha-lactalbumin (LA), the Gal acceptor specificity is altered from GlcNAc to Glc. Gal-T1 also transfers GalNAc ...

    beta1,4-Galactosyltransferase I (Gal-T1) normally transfers Gal from UDP-Gal to GlcNAc in the presence of Mn(2+) ion. In the presence of alpha-lactalbumin (LA), the Gal acceptor specificity is altered from GlcNAc to Glc. Gal-T1 also transfers GalNAc from UDP-GalNAc to GlcNAc, but with only approximately 0.1% of Gal-T activity. To understand this low GalNAc-transferase activity, we have carried out the crystal structure analysis of the Gal-T1.LA complex with UDP-GalNAc at 2.1-A resolution. The crystal structure reveals that the UDP-GalNAc binding to Gal-T1 is similar to the binding of UDP-Gal to Gal-T1, except for an additional hydrogen bond formed between the N-acetyl group of GalNAc moiety with the Tyr-289 side chain hydroxyl group. Elimination of this additional hydrogen bond by mutating Tyr-289 residue to Leu, Ile, or Asn enhances the GalNAc-transferase activity. Although all three mutants exhibit enhanced GalNAc-transferase activity, the mutant Y289L exhibits GalNAc-transferase activity that is nearly 100% of its Gal-T activity, even while completely retaining its Gal-T activity. The steady state kinetic analyses on the Leu-289 mutant indicate that the K(m) for GlcNAc has increased compared to the wild type. On the other hand, the catalytic constant (k(cat)) in the Gal-T reaction is comparable with the wild type, whereas it is 3-5-fold higher in the GalNAc-T reaction. Interestingly, in the presence of LA, these mutants also transfer GalNAc to Glc instead of to GlcNAc. The present study demonstrates that, in the Gal-T family, the Tyr-289/Phe-289 residue largely determines the sugar donor specificity.


    Organizational Affiliation

    Structural Glycobiology Section and Intramural Research Support Program-SAIC, 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 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MN
Query on MN

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

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Download CCD File 
A, C
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
UD2
Query on UD2

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B, D
URIDINE-DIPHOSPHATE-N-ACETYLGALACTOSAMINE
(2R,3R,4R,5R,6R)-3-(acetylamino)-4,5-dihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl [(2R,3S,4R,5R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-3,4-dihydroxytetrahydrofuran-2-yl]methyl dihydrogen diphosphate
C17 H27 N3 O17 P2
LFTYTUAZOPRMMI-NESSUJCYSA-N
 Ligand Interaction
PG4
Query on PG4

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A, B
TETRAETHYLENE GLYCOL
C8 H18 O5
UWHCKJMYHZGTIT-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Free: 0.244 
  • R-Value Work: 0.194 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 57.471α = 90.00
b = 95.677β = 101.40
c = 100.581γ = 90.00
Software Package:
Software NamePurpose
CNSrefinement
DENZOdata reduction
AMoREphasing
SCALEPACKdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-03-18
    Type: Initial release
  • Version 1.1: 2007-10-16
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance