The dNTPase enzyme activity is inhibited by nucleic acids and contains a heat-insensitive component

The dNTpase enzyme has previously been shown to specifically hydrolyse monodeoxyribonucleoside triphosphates (dNTPs). The remnant nucleotide resulting from this hydrolysis lacks the terminal phosphate and is covalently attached as part of a 3 kDa species, which we have termed the product nucleotide binding particle or "PNBP." PNBP is resistant to numerous nucleases and RNases, suggesting that it is not a nucleic acid polymer. Given that the exclusive specificity of dNTPase for dNTPs suggests some associative cellular role for the enzyme in polynucleotide maintenance, the interaction of dNTPase with various nucleic acids has now been examined. It is demonstrated that dNTPase activity is significantly inhibited by addition of single-stranded DNA or tRNA, but not rRNA. The data presented also suggest that thio-dATP can substitute for conventional phosphoester dATP in the enzymatic reaction. It is also demonstrated that the dNTPase enzyme comprises both heat/proteolysis/denaturant stable and heat/proteolysis/denaturant-sensitive components and we propose that this stable component may be the precursor to liganded PNBP.