Altered subunit communication in subfamilies of trimeric dUTPases

The enzyme dUTPase is essential in preventing uracil incorporation into DNA . Design of antagonists against this novel chemotherapeutic target requires identification of species-specific differences in the structure and mechan ism of the enzyme. This task is now approached via comparisons of available crystallographic structures of dUTPases from Homo sapiens, Escherichia col i, and retroviruses. The eukaryotic protein uniquely displays polar and cha rged amino acid residues participating in threefold intersubunit interactio ns. In bacterial and retroviral dUTPases, threefold interactions are mainly hydrophobic. The residues responsible for this contrast are mapped in mult iple sequence alignment to positions differently and characteristically con served in distinct evolutionary branches. The general feature of this contr ast is further strengthened by a second eukaryotic model structure construc ted using comparative modeling. The dUTPase cDNA from Drosophila melanogast er was identified, sequenced, and the model structure of the encoded polype ptide displayed a polar hydrogen-bonding network of threefold interactions, identically to the human structure. Results allow clear distinction betwee n two subfamilies of trimeric dUTPases where altered subunit communication may account for a functional difference in the catalytic cycle. (C) 2000 Ac ademic Press.