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CSA entry for 1foa
Original Entry
Title:
Transferase
Compound:
Alpha-1,3-mannosyl-glycoprotein beta-1,2-n- acetylglucosaminyltransferase
Mutant:
No
UniProt/Swiss-Prot:
P27115-GNT1_RABIT
EC Class:
2.4.1.101
Other CSA Entries:
Overview of all sites for 1foa
Homologues of 1foa
Entries for UniProt/Swiss-Prot: P27115
Entries for EC: 2.4.1.101
Other Databases:
PDB entry: 1foa
PDBsum entry: 1foa
UniProt/Swiss-Prot: P27115
IntEnz entry: 2.4.1.101
Literature Report:
Introduction:
N-acetylglucosaminyltransferase I (GnT I) is from Oryctolagus cuniculus. It catalyses the attachment of N-acetyl glucosamine (GlcNAc) onto an oligomannose core, from UPD-N-acetyl glucosamine. It plays a critical role in mammalian development.
Mechanism:
1. Asp 291 acts as a general base to deprotonate a hydroxyl group of the oligomannose core sugar.
2. The deprotonated oxygen atom then acts as a nucleophile and attacks C1 of UPD-N-acetyl glucosamine.
3. The transition state is thought to be oxocarbenium ion-like.
4. The C1 - UPD bond is broken, leaving the n-acetyl glucosamine bonded to the oligomannose core.
5. Mn2+ stabilises the build up of negative charge on the beta-phosphate of the UPD.
6. It is thought that Asp 291 then acts as an acid to protonate the UPD leaving group.
Sites:

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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ASPA 291 291Sidechain
Acid/baseSubstrate
Asp 291 acts as a general base by accepting a proton from a hydroxyl group on the oligamannose core. It must then donate that proton back to the leaving group UPD phosphate ion.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11032794 Current protein Residue is positioned appropriately (ligand position known)
PubMed ID 11032794 Current protein Structural similarity to homologue of known mechanism

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
MNA 448 0
ElectrostaticSubstrate
Mn2+ stabilises the negative charge that develops on the beta-phosphate of the UPD leaving group.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11032794 Current protein Structural similarity to homologue of known mechanism
Notes:

References:
1
X-ray crystal structure of rabbit N-acetylglucosaminyltransferase I: catalytic mechanism and a new protein superfamily.
U. M. Unligil and S. Zhou and S. Yuwaraj and M. Sarkar and H. Schachter and J. M. Rini
EMBO J 19, (20) 5269-80, (2000).
11032794
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