Glycine rich P-loop motif in deoxyuridine pyrophosphatase

Deoxyuridine pyrophosphatase (dUTPase) cleaves the alpha-beta phosphodiester bond of dUTP to form pyrophosphate and dUMP, preventing incorporation of uracil into DNA and providing the substrate for dTTP synthesis. Similar to other nucleotide binding proteins, dUTPase also consists of a sequence motif rich in glycine residues known as P-loop motif. The P-loo motif of the nucleotide binding proteins are involved in substrate binding, catalysis, recognition and regulation of activity. In dUTPase the function of the P-loop motif is not well understood. One of the main reasons for this limited information is the lack of the three-dimensional structure of a dUTPase enzyme with an ordered Gly-rich P-loop motif with a bound substrate and Mg2+ ion. This review presents an insight into the role of Gly-rich P-loop motif in the function of dUTPase as revealed from the crystal structure. The analysis reveals the Gly-rich P-loop motif of dUTPase to be the longest in terms of its amino-acid composition as compared to other nucleotide binding proteins and exhibit a high-degree of sequence conservation among spectrum of species. The enzyme utilizes adaptive recognition to bind to the phosphate groups of the nucleotide. In particular, the oc-P phosphodiester bond adopts an unfavorable eclipsed conformation in the presence of the Gly-rich P-loop motif. This conformation may be relevant to the mechanism of a-P phosphodiester bond cleavage.