The Gly-Arg-rich C-terminal domain of pea nucleolin is a DNA helicase that catalytically translocates in the 5'- to 3'-direction.
Nucleolin is a major nucleolar phosphoprotein of exponentially growing eukaryotic cells. Here we report the cloning, purification, and characterization of the C-terminal glycine/arginine-rich (GAR) domain of pea nucleolin. The purified recombinant protein (17 kDa) shows ATP-/Mg(2+)-dependent DNA helicase and ssDNA-/Mg(2+)-dependent ATPase activities. The enzyme unwinds DNA in the 5'- to 3'-direction, which is the first report in plant for this directional activity. It unwinds forked/non-forked DNA with equal efficiency. The anti-nucleolin antibodies immunodepleted the activities of the enzyme. The DNA interacting ligands nogalamycin, daunorubicin, actinomycin C1, and ethidium bromide were inhibitory to DNA unwinding (with K(i) values of 0.40, 2.21, 8.0, and 9.0 microM, respectively) and ATPase (with K(i) values of 0.43, 1.65, 4.6, and 7.0 microM, respectively) activities of the enzyme. This study confirms that the unwinding and ATPase activities of pea nucleolin resided in the GAR domain. This study should make important contribution to our better understanding of DNA transaction in plants, mechanism of DNA unwinding, and the mechanism by which these ligands can disturb genome integrity.
Nasirudin
Khondaker M
KM
Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110 067, India.
Ehtesham
Nasreen Z
NZ
Tuteja
Renu
R
Sopory
Sudhir K
SK
Tuteja
Narendra
N
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D004265:DNA Helicases / Q000737:chemistry*; D018076:DNA, Complementary / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry; D003609:Dactinomycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D003630:Daunorubicin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004996:Ethidium / Q000494:pharmacology; D007700:Kinetics; D008957:Models, Genetic; D009621:Nogalamycin / Q000494:pharmacology; D018532:Pisum sativum / Q000201:enzymology / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D011108:Polymers / Q000737:chemistry; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D013696:Temperature; D014466:Ultraviolet Rays; D000097796:Nucleolin
D000251:Adenosine Triphosphatases; D004247:DNA; D004265:DNA Helicases; D018076:DNA, Complementary; D004277:DNA, Single-Stranded; D003609:Dactinomycin; D003630:Daunorubicin; D004996:Ethidium; D009621:Nogalamycin; D010750:Phosphoproteins; D011108:Polymers; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000097796:Nucleolin; C030013:cactinomycin