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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1vie
Original Entry
Title:
Oxidoreductase
Compound:
Dihydrofolate reductase
Mutant:
No
UniProt/Swiss-Prot:
P00383-DY21_ECOLI
EC Class:
1.5.1.3
Other CSA Entries:
Overview of all sites for 1vie
Homologues of 1vie
Entries for UniProt/Swiss-Prot: P00383
Entries for EC: 1.5.1.3
Other Databases:
PDB entry: 1vie
PDBsum entry: 1vie
UniProt/Swiss-Prot: P00383
IntEnz entry: 1.5.1.3
Literature Report:
Introduction:
R67-plasmid encoded dihydrofolate reductase (R67-DHFR) from Escherichia coli catalyses the reduction of 7,8-dihydrofolate (DHF) to 5,6,7,8-tetrahydrofolate (THF) in the presence of NADPH. It is one of the smallest enzymes known to self-assemble into an active quaternary structure. The tetramer has an unusual pore, 25 angstroms in length that passes through the middle of the molecule and out the other side. R67-DHFR has 222 symmetry, and has a distinctive 'one site fits both' substrate and cofactor.
Mechanism:
The mechanism of R67-DHFR relies on a pre-protonated form of DHF being the substrate. The substrate then accepts a hydride from NADPH to form the product, THF. The catalytic residues Tyr 69, Ile 68 and Gln 67 destabilise the ground state. Lys 32 is involved in stabilising the transition state.
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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
LYSA 32 32Sidechain
ElectrostaticSubstrate
The positively charged sidechain of Lys 32 helps to stabilise the negatively charged intermediate.
Evidence from paper Evidence concerns Evidence type
PubMed ID 15812782 Current protein Mutagenesis of residue
PubMed ID 15812782 Current protein Computer modelling

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
GLNA 67 67Sidechain
ElectrostaticSubstrate
Gln 67 acts to destabilise the ground state of the substrate.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11560482 Current protein Mutagenesis of residue
PubMed ID 11560482 Current protein Kinetic studies

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ILEA 68 68Sidechain
ElectrostaticSubstrate
Ile 68 acts to destabilise the ground state.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11560482 Current protein Kinetic studies
PubMed ID 11560482 Current protein Mutagenesis of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
TYRA 69 69Sidechain
ElectrostaticSubstrate
Tyr 69 acts to destabilise the ground state.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11560482 Current protein Mutagenesis of residue
PubMed ID 11560482 Current protein Kinetic studies
Notes:
It is not exactly known how these residues stabilise the transition state or destabilise the ground state.
References:
1
Searching sequence space: two different approaches to dihydrofolate reductase catalysis.
E. E. Howell
Chembiochem 6, (4) 590-600, (2005).
15812782
2
Role of S65, Q67, I68, and Y69 residues in homotetrameric R67 dihydrofolate reductase.
M. B. Strader and R. D. Smiley and L. G. Stinnett and N. C. VerBerkmoes and E. E. Howell
Biochemistry 40, (38) 11344-52, (2001).
11560482
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