3FRO

Crystal structure of Pyrococcus abyssi glycogen synthase with open and closed conformations


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.5 Å
  • R-Value Free: 0.255 
  • R-Value Work: 0.214 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Lyase activity of glycogen synthase: Is an elimination/addition mechanism a possible reaction pathway for retaining glycosyltransferases?

Diaz, A.Diaz-Lobo, M.Grados, E.Guinovart, J.J.Fita, I.Ferrer, J.C.

(2012) IUBMB Life 64: 649-658

  • DOI: 10.1002/iub.1048

  • PubMed Abstract: 
  • Despite the biological relevance of glycosyltrasferases (GTs) and the many efforts devoted to this subject, the catalytic mechanism through which a subclass of this large family of enzymes, namely those that operate with net retention of the anomeric ...

    Despite the biological relevance of glycosyltrasferases (GTs) and the many efforts devoted to this subject, the catalytic mechanism through which a subclass of this large family of enzymes, namely those that operate with net retention of the anomeric configuration, has not been fully established. Here, we show that in the absence of an acceptor, an archetypal retaining GT such as Pyrococcus abyssi glycogen synthase (PaGS) reacts with its glucosyl donor substrate, uridine 5'-diphosphoglucose (UDP-Glc), to produce the scission of the covalent bond between the terminal phosphate oxygen of UDP and the sugar ring. X-ray diffraction analysis of the PaGS/UDP-Glc complex shows no electronic density attributable to the UDP moiety, but establishes the presence in the active site of the enzyme of a glucose-like derivative that lacks the exocyclic oxygen attached to the anomeric carbon. Chemical derivatization followed by gas chromatography/mass spectrometry of the isolated glucose-like species allowed us to identify the molecule found in the catalytic site of PaGS as 1,5-anhydro-D-arabino-hex-1-enitol (AA) or its tautomeric form, 1,5-anhydro-D-fructose. These findings are consistent with a stepwise S(N) i-like mechanism as the modus operandi of retaining GTs, a mechanism that involves the discrete existence of an oxocarbenium intermediate. Even in the absence of a glucosyl acceptor, glycogen synthase (GS) promotes the formation of the cationic intermediate, which, by eliminating the proton of the adjacent C2 carbon atom, yields AA. Alternatively, these observations could be interpreted assuming that AA is a true intermediate in the reaction pathway of GS and that this enzyme operates through an elimination/addition mechanism.


    Organizational Affiliation

    Institute for Research in Biomedicine, IRB Barcelona.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
GlgA glycogen synthase
A, B, C
439Pyrococcus abyssi (strain GE5 / Orsay)Mutation(s): 0 
Find proteins for Q9V2J8 (Pyrococcus abyssi (strain GE5 / Orsay))
Go to UniProtKB:  Q9V2J8
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PO4
Query on PO4

Download SDF File 
Download CCD File 
A, B, C
PHOSPHATE ION
O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-K
 Ligand Interaction
NHF
Query on NHF

Download SDF File 
Download CCD File 
B
1,5-anhydro-D-fructose
C6 H10 O5
OCLOLUFOLJIQDC-HSUXUTPPSA-N
 Ligand Interaction
TRS
Query on TRS

Download SDF File 
Download CCD File 
A, B
2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL
TRIS BUFFER
C4 H12 N O3
LENZDBCJOHFCAS-UHFFFAOYSA-O
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.5 Å
  • R-Value Free: 0.255 
  • R-Value Work: 0.214 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 74.998α = 90.00
b = 139.913β = 90.00
c = 159.414γ = 90.00
Software Package:
Software NamePurpose
SCALAdata scaling
MOLREPphasing
PDB_EXTRACTdata extraction
MOSFLMdata reduction
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2010-01-12
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Advisory, Version format compliance
  • Version 1.2: 2017-11-01
    Type: Database references