Molecular characterization of Plasmodium falciparum putative polynucleotide kinase/phosphatase

• Published in: Molecular and biochemical parasitology 2011-11, Vol.180 (1), p.1-7
• Main Authors: Siribal, Saranya, Weinfeld, Michael, Karimi-Busheri, Feridoun, Mark Glover, J.N., Bernstein, Nina K., Aceytuno, Danny, Chavalitshewinkoon-Petmitr, Porntip
• Format: Article
• Language: English
• Subjects: 3′-Phosphatase; 5′-Kinase; Amino Acid Sequence; DNA; DNA repair; enzyme activity; Enzyme Stability; Escherichia coli; genes; Humans; Molecular Sequence Data; Nucleotidases - chemistry; Nucleotidases - genetics; Nucleotidases - metabolism; nucleotides; parasites; parasitology; Plasmodium falciparum; Plasmodium falciparum - chemistry; Plasmodium falciparum - enzymology; Plasmodium falciparum - genetics; Polynucleotide 5'-Hydroxyl-Kinase - chemistry; Polynucleotide 5'-Hydroxyl-Kinase - genetics; Polynucleotide 5'-Hydroxyl-Kinase - metabolism; Polynucleotide kinase/phosphatase; Protein Structure, Tertiary; proteins; Sequence Alignment; Substrate Specificity
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/j.molbiopara.2011.06.007

[Display omitted] ► Polynucleotide kinase/phosphatase gene of Plasmodium falciparum was cloned and expressed. ► 3′-Phosphatase activity was detected but 5′ kinase activity was not observed. ► The enzyme use only single-stranded substrates, and not double-stranded substrates. ► PfPNKP is more sensitive to sodium vanadate (Na3VO4) than human PNKP. ► Unlike human PNKP, PfPNKP is involved in single-strand breaks repair. Polynucleotide kinase/phosphatase (PNKP) is a bifunctional enzyme that can phosphorylate the 5′-OH termini and dephosphorylate the 3′-phosphate termini of DNA. It is a DNA repair enzyme involved in the processing of strand break termini, which permits subsequent repair proteins to replace missing nucleotides and rejoin broken strands. Little is known about DNA repair in Plasmodium falciparum, including the roles of PNKP in repairing parasite DNA. We identified a P. falciparum gene encoding a protein with 24% homology to human PNKP and thus suggestive of a putative PNKP. In this study, the PNKP gene of P. falciparum strain K1 (PfPNKP) was successfully cloned and expressed in E. coli as a GST-PfPNKP recombinant protein. MALDI-TOF/TOF analysis of the protein confirmed the identity of PfPNKP. Assays for enzymatic activity were carried out with a variety of single- and double-stranded substrates. Although 3′-phosphatase activity was detected, PfPNKP was observed to dephosphorylate single-stranded substrates or double-stranded substrates with a short 3′-single-stranded overhang, but not double-stranded substrates that mimicked single-strand breaks. We hypothesize that unlike human PNKP, PfPNKP may not be involved in single-strand break repair, since alternative terminal processing mechanisms can substitute for PfPNKP, and that PfPNKP DNA repair actions may be confined to overhanging termini of double-strand breaks.