The flexible motif V of Epstein-Barr virus deoxyuridine 5'-triphosphate pyrophosphatase is essential for catalysis.
Deoxyuridine 5'-triphosphate pyrophosphatases (dUTPases) are ubiquitous enzymes essential for hydrolysis of dUTP, thus preventing its incorporation into DNA. Although Epstein-Barr virus (EBV) dUTPase is monomeric, it has a high degree of similarity with the more frequent trimeric form of the enzyme. In both cases, the active site is composed of five conserved sequence motifs. Structural and functional studies of mutants based on the structure of EBV dUTPase gave new insight into the mechanism of the enzyme. A first mutant allowed us to exclude a role in enzymatic activity for the disulfide bridge involving the beginning of the disordered C terminus. Sequence alignments revealed two groups of dUTPases, based on the position in sequence of a conserved aspartic acid residue close to the active site. Single mutants of this residue in EBV dUTPase showed a highly impaired catalytic activity, which could be partially restored by a second mutation, making EBV dUTPase more similar to the second group of enzymes. Deletion of the flexible C-terminal tail carrying motif V resulted in a protein completely devoid of enzymatic activity, crystallizing with unhydrolyzed Mg(2+)-dUTP complex in the active site. Point mutations inside motif V highlighted the essential role of lid residue Phe(273). Magnesium appears to play a role mainly in substrate binding, since in absence of Mg(2+), the K(m) of the enzyme is reduced, whereas the k(cat) is less affected.
Freeman
Lucy
L
Unit of Virus Host Cell Interactions UMI3265 UJF-EMBL-CNRS, University of Grenoble, F-38042 Grenoble Cedex 9, France.
Buisson
Marlyse
M
Tarbouriech
Nicolas
N
Van der Heyden
Angéline
A
Labbé
Pierre
P
Burmeister
Wim P
WP
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D004854:Herpesvirus 4, Human / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D011755:Pyrophosphatases / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D011755:Pyrophosphatases; C020020:dUTP pyrophosphatase; D008274:Magnesium