Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In our previous study, we identified four chromatographically distinct DNA-dependent ATPases, B, C1, C2, and C3, in mouse FM3A cells (Tawaragi, Y., Enomoto, T., Watanabe, Y., Hanaoka, F., and Yamada, M. (1984) Biochemistry 23, 529-533). The DNA-dependent ATPase C1 has been purified and characterized in detail. A divalent cation and a polynucleotide cofactor were required for the ATPase activity. Poly(dT), single-stranded circular DNA, and heat-denatured DNA were very effective. Almost no ATPase activity was observed with S1 nuclease-treated native DNA. ATPase C1 hydrolyzed ATP only among the ribo- and deoxyribonucleoside triphosphates tested, and this fact distinguished ATPase C1 from ATPases B, C2, and C3, because the latter enzymes are capable of hydrolyzing both ATP and dATP. The purified DNA-dependent ATPase C1 fraction was shown to have a DNA helicase activity that was dependent on hydrolysis of ATP. The helicase activity and DNA-dependent ATPase activity cosedimented at 5.2 S on glycerol gradient centrifugation. Both activities showed similar preferences for nucleoside 5'-triphosphates and similar requirements for divalent cations. The DNA helicase activity was inhibited by the addition of single-stranded DNAs that served as cofactor for the ATPase activity. The efficiency of a single-stranded DNA to inhibit DNA helicase activity correlated well with the capacity of the DNA to serve as cofactor for DNA-dependent ATPase activity. The helicase was shown to migrate along the DNA strand in the 5' to 3' direction, which is the same direction of migration of the mouse DNA helicase B (Seki, M., Enomoto, T., Yanagisawa, J., Hanaoka, F., and Ui, M. (1988) Biochemistry 27, 1766-1771).
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PMID:DNA-dependent adenosinetriphosphatase C1 from mouse FM3A cells has DNA helicase activity. 131 Sep 78

At least six DNA helicases have been identified during fractionation of extracts from the yeast Saccharomyces cerevisiae. Three of those, DNA helicases B, C, and D, have been further purified and characterized. DNA helicases B and C co-purified with DNA polymerase delta through several chromatographic steps, but were separated from the polymerase by hydrophobic chromatography. DNA helicase D co-purified with Replication Factor C over seven chromatographic steps, and was only separated from it by glycerol gradient centrifugation in the presence of 0.2 M NaCl. All three helicases are DNA dependent ATPases with Km values for ATP of 190 microM, 325 microM, and 60 microM for DNA helicases B, C, and D, respectively. Their DNA helicase activities are comparable. They are 5'-3' helicases and have pH optima of 6.5-7 and Mg2+ optima of 1-2 mM. However, they differ in the nucleotide requirement for helicase action. Whereas all three helicases preferred ATP, dATP, UTP, CTP, and dCTP as cofactors, DNA helicase C also used GTP, but not dTTP. On the other hand, DNA helicase D used dTTP, but not GTP, and DNA helicase B used neither nucleotide as cofactor. These studies allowed us to conclude that DNA helicases B, C, and D are not only distinct enzymes, but also different from two previously identified yeast DNA helicases, the RAD3 protein and ATPase III.
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PMID:Three new DNA helicases from Saccharomyces cerevisiae. 133 84

The DNA helicase activity of DNA-dependent ATPase B purified from mouse FM3A cells [Seki, M., Enomoto, T., Hanaoka, F., & Yamada, M. (1987) Biochemistry 26, 2924-2928] has been further characterized. The helicase activity was assayed with partially duplex DNA substrates in which oligonucleotides to be released by the enzyme were radiolabeled. Oligonucleotides with or without phosphate at the 5' termini or with a deoxy- or dideoxyribose at the 3'-terminal nucleotides were displaced by this enzyme with essentially the same efficiency and with the same ATP (and dATP) and Mg2+ requirements. Thus, there was no strict structure requirement for both ends of duplex regions of substrates to be unwound by the enzyme. Shorter strands were released more readily than longer strands up to the length of 140 bases. The attachment of the enzyme to a single-stranded DNA region was a prerequisite for the neighboring duplex to be unwound; the enzyme-catalyzed unwinding was inhibited competitively by the coaddition of single-stranded DNAs which act as cofactors of the ATPase activity. Their activities as the inhibitor of helicase were well correlated with those as the cofactor of ATPase. The helicase B was found to migrate along single-stranded DNA in the 5' to 3' direction by the use of single strands with short duplex regions at both 3' and 5' ends as substrate. A possible role of this enzyme in DNA replication in mammalian cells is discussed.
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PMID:Further characterization of DNA helicase activity of mouse DNA-dependent adenosinetriphosphatase B (DNA helicase B). 296 39

Many prokaryotic and viral DNA helicases involved in DNA replication stimulate their cognate DNA primase activity. To assess the stimulation of DNA primase activity by mammalian DNA helicases, we analyzed the synthesis of oligoribonucleotides by mouse DNA polymerase alpha-primase complex on single-stranded circular M13 DNA in the presence of mouse DNA helicase B. DNA helicase B was purified by sequential chromatography through eight columns. When the purified DNA helicase B was applied to a Mono Q column, the stimulatory activity for DNA primase-catalyzed oligoribonucleotide synthesis and DNA helicase and DNA-dependent ATPase activities of DNA helicase B were co-eluted from the column. The synthesis of oligoribonucleotides 5-10 nt in length was markedly stimulated by DNA helicase B. The synthesis of longer species of oligoribonucleotides, which were synthesized at a low level in the absence of DNA helicase B, was inhibited by DNA helicase B. The stimulatory effect of DNA helicase B was marked at low template concentrations and little or no effect was observed at high concentrations. The mouse single-stranded DNA binding protein, replication protein A (RP-A), inhibited the primase activity of the DNA polymerase alpha-primase complex and DNA helicase B partially reversed the inhibition caused by RP-A.
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PMID:Stimulation of mouse DNA primase-catalyzed oligoribonucleotide synthesis by mouse DNA helicase B. 759 31

A temperature-sensitive mutant defective in DNA replication, tsFT848, was isolated from the mouse mammary carcinoma cell line FM3A. In mutant cells, the DNA-dependent ATPase activity of DNA helicase B, which is a major DNA-dependent ATPase in wild-type cells, decreased at the nonpermissive temperature of 39 degrees C. DNA synthesis in tsFT848 cells at the nonpermissive temperature was analyzed in detail. DNA synthesis measured by incorporation of [3H]thymidine decreased to about 50% and less than 10% of the initial level at 8 and 12 h, respectively. The decrease in the level of thymidine incorporation correlated with a decrease in the number of silver grains in individual nuclei but not with the number of cells with labeled nuclei. DNA fiber autoradiography revealed that the DNA chain elongation rate did not decrease even after an incubation for 10 h at 39 degrees C, suggesting that initiation of DNA replication at the origin of replicons is impaired in the mutant cells. The decrease in DNA-synthesizing ability coincided with a decrease in the level of the DNA-dependent ATPase activity of DNA helicase B. Partially purified DNA helicase B from tsFT848 cells was more heat sensitive than that from wild-type cells. Inactivation of DNA-dependent ATPase activity of DNA helicase B from mutant cells was considerably reduced by adding DNA to the medium used for preincubation, indicating that the DNA helicase of mutant cells is stabilized by binding to DNA.
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PMID:Characterization of DNA synthesis and DNA-dependent ATPase activity at a restrictive temperature in temperature-sensitive tsFT848 cells with thermolabile DNA helicase B. 779 22

We have purified a DNA dependent ATPase/DNA helicase, DNA helicase B, from S. cerevisiae. Helicase B was a 129-kDa polypeptide. The ATPase activity of helicase B was strongly DNA dependent. The DNA helicase activity was stimulated by yeast replication protein A, indicating a probable function in DNA replication. Helicase B showed a 5'-->3' polarity of movement. Protein sequencing indicated that helicase B was identical to a hypothetical 127-kDa polypeptide encoded by yORF61, located 5' upstream of the BMH1 locus in chromosome V. The protein sequence contained a "type I ATP/GTP binding motif" and other helicase-like motifs and the expressed protein exhibited helicase activity. Thus, we concluded that yORF61 is the gene for helicase B and will be referred to as HCSB.
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PMID:Biochemical and genetic characterization of a replication protein A dependent DNA helicase from the yeast, Saccharomyces cerevisiae. 783 96

A cDNA encoding a human ortholog of mouse DNA helicase B, which may play a role in DNA replication, has been cloned and expressed as a recombinant protein. The predicted human DNA helicase B (HDHB) protein contains conserved helicase motifs (superfamily 1) that are strikingly similar to those of bacterial recD and T4 dda proteins. The HDHB gene is expressed at low levels in liver, spleen, kidney, and brain and at higher levels in testis and thymus. Purified recombinant HDHB hydrolyzed ATP and dATP in the presence of single-stranded DNA, displayed robust 5'-3' DNA helicase activity, and interacted physically and functionally with DNA polymerase alpha-primase. HDHB proteins with mutations in the Walker A or B motif lacked ATPase and helicase activity but retained the ability to interact with DNA polymerase alpha-primase, suggesting that the mutants might be dominant over endogenous HDHB in human cells. When purified HDHB protein was microinjected into the nucleus of cells in early G(1), the mutant proteins inhibited DNA synthesis, whereas the wild type protein had no effect. Injection of wild type or mutant protein into cells at G(1)/S did not prevent DNA synthesis. The results suggest that HDHB function is required for S phase entry.
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PMID:A dominant-negative mutant of human DNA helicase B blocks the onset of chromosomal DNA replication. 1218 27