Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rad3 protein from the yeast Saccharomyces cerevisiae is a single-stranded DNA-dependent ATPase which catalyzes the unwinding of DNA.DNA duplexes. In the present studies we have demonstrated that the purified enzyme additionally catalyzes the displacement of RNA fragments annealed to complementary DNA. Quantitative comparisons using otherwise identical partially duplex DNA.DNA and DNA.RNA substrates indicate a significant preference for the latter. Competition for ATPase or DNA helicase activity by various homopolymers suggests that Rad3 protein does not discriminate between ribonucleotide and deoxyribonucleotide homopolymers with respect to binding. However, neither single-stranded RNA nor various ribonucleotide homopolymers supported the hydrolysis of nucleoside 5'-triphosphates. Additionally, Rad3 protein was unable to catalyze the displacement of oligo(dA) annealed to poly(U), suggesting that the catalytic domain of the enzyme is exquisitely sensitive to chemical and/or or conformational differences between DNA and RNA. Hence, it appears that Rad3 protein is not an RNA helicase.
...
PMID:Substrate specificity of the Rad3 ATPase/DNA helicase of Saccharomyces cerevisiae and binding of Rad3 protein to nucleic acids. 131 9

eIF-4A is a translation initiation factor that exhibits bidirectional RNA unwinding activity in vitro in the presence of another translation initiation factor, eIF-4B and ATP. This activity is thought to be responsible for the melting of secondary structure in the 5' untranslated region of eukaryotic mRNAs to facilitate ribosome binding. eIF-4A is a member of a fast growing family of proteins termed the DEAD family. These proteins are believed to be RNA helicases, based on the demonstrated in vitro RNA helicase activity of two members (eIF-4A and p68) and their homology in eight amino acid regions. Several related biochemical activities were attributed to eIF-4A: (i) ATP binding, (ii) RNA-dependent ATPase and (iii) RNA helicase. To determine the contribution of the highly conserved regions to these activities, we performed site-directed mutagenesis. First we show that recombinant eIF-4A, together with recombinant eIF-4B, exhibit RNA helicase activity in vitro. Mutations in the ATPase A motif (AXXXXGKT) affect ATP binding, whereas mutations in the predicted ATPase B motif (DEAD) affect ATP hydrolysis. We report here that the DEAD region couples the ATPase with the RNA helicase activity. Furthermore, two other regions, whose functions were unknown, have also been characterized. We report that the first residue in the HRIGRXXR region is involved in ATP hydrolysis and that the SAT region is essential for RNA unwinding. Our results suggest that the highly conserved regions in the DEAD box family are critical for RNA helicase activity.
...
PMID:Mutational analysis of a DEAD box RNA helicase: the mammalian translation initiation factor eIF-4A. 137 97

The seven conserved motifs typical of the helicase superfamily II have been identified in the sequences of Escherichia coli protein SecA, an ATPase mediating protein translocation across the inner membrane of the bacterium, and its Bacillus subtilis homolog Div. It is hypothesized that SecA and Div possess an RNA helicase activity and may couple ATP hydrolysis both to membrane translocation of proteins, and to hairpin unwinding in their own mRNAs, leading to the known autogenous regulation of translation.
...
PMID:Autogenous translation regulation by Escherichia coli ATPase SecA may be mediated by an intrinsic RNA helicase activity of this protein. 153 61

The RAD3 gene of Saccharomyces cerevisiae is required for excision repair and is essential for cell viability. RAD3 encoded protein possesses a single stranded DNA-dependent ATPase and DNA and DNA.RNA helicase activities. Mutational studies have indicated a requirement for the RAD3 helicase activities in excision repair. To examine the extent of conservation of structure and function of RAD3 during eukaryotic evolution, we have cloned the RAD3 homolog, rhp3+, from the distantly related yeast Schizosaccharomyces pombe. RAD3 and rhp3+ encoded proteins are highly similar, sharing 67% identical amino acids. We show that like RAD3, rhp3+ is indispensable for excision repair and cell viability, and our studies indicate a requirement of the putative rhp3+ DNA helicase activity in DNA repair. We find that the RAD3 and rhp3+ genes can functionally substitute for one another. The level of complementation provided by the rhp3+ gene in S.cerevisiae rad3 mutants or by the RAD3 gene in S.pombe rhp3 mutants is remarkable in that both the excision repair and viability defects in both yeasts are restored to wild type levels. These observations suggest a parallel evolutionary conservation of other protein components with which RAD3 interacts in mediating its DNA repair and viability functions.
...
PMID:The Schizosaccharomyces pombe rhp3+ gene required for DNA repair and cell viability is functionally interchangeable with the RAD3 gene of Saccharomyces cerevisiae. 153 6

An RNA helicase, isolated from nuclear extracts of HeLa cells, displaced duplex RNA in the presence of any one of the eight common nucleoside triphosphates. The unwinding reaction was supported most efficiently by ATP and GTP and poorly by dCTP and dTTP. The enzyme activity, purified 300-fold, contained two major protein bands of 80 and 55 kDa when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All fractions that contained RNA helicase activity also possessed single-stranded RNA-dependent nucleoside triphosphatase activity. Purified RNA helicase fractions displaced a hybrid of U4/U6 RNAs with the same efficiency as it displaced other duplex RNA structures. In contrast, the RNA helicase did not displace duplex RNA/DNA and DNA/DNA structures. Evidence is presented that suggests that this RNA helicase can displace duplex RNA by translocating in both the 3' to 5' and the 5' to 3' directions. The properties of the RNA helicase described here differ from the deaminase RNA unwinding activity described in Xenopus oocytes (Bass, B.L., and Weintraub, H. (1987) Cell 48, 607-613) and from the p68 HeLa RNA helicase (Hirling, H., Scheffner, M., Restle, T., and Stahl, H. (1989) Nature 339, 562-564).
...
PMID:The isolation and characterization of an RNA helicase from nuclear extracts of HeLa cells. 170 30

Recently it has been reported that a membrane fraction can be isolated from West Nile virus-infected BHK cells which contains the viral nonstructural (NS) proteins as major constituents (Wengler et al., 1990). In this report we show that treatment of these membranes with subtilisin releases the carboxy-terminal segment of the NS 3 protein as a soluble protein of about 50 kDa apparent molecular weight. This molecule, which is called the p50-S protein, can be purified by standard chromatographic procedures. The p50-S protein binds to poly(A) and apparently represents a nucleoside triphosphatase which is stimulated in the presence of ssRNA molecules. The data represent experimental support for the predicted role of this segment of the NS 3 protein as an RNA helicase. Some properties of the p50-S protein are described and a possible function of this protein segment during RNA synthesis is discussed.
...
PMID:The carboxy-terminal part of the NS 3 protein of the West Nile flavivirus can be isolated as a soluble protein after proteolytic cleavage and represents an RNA-stimulated NTPase. 171 26

The RAD3 gene of Saccharomyces cerevisiae is required for excision repair of UV-damaged DNA and is essential for cell viability. The RAD3 protein exhibits a remarkable degree of sequence homology to the human excision repair protein ERCC2. The RAD3 protein is a single-stranded DNA-dependent ATPase and a DNA helicase capable of denaturing long regions of duplex DNA. Here, we demonstrate that RAD3 also possesses a potent DNA.RNA helicase activity similar in efficiency to its DNA helicase activity. The rad3 Arg-48 mutant protein, which binds but does not hydrolyze ATP, lacks the DNA.RNA unwinding activity, indicating a dependence on ATP hydrolysis. RAD3 does not show any RNA-dependent NTPase activity and, as expected, does not unwind duplex RNA. This observation suggests that RAD3 translocates on DNA in unwinding DNA.RNA duplexes. That the rad3 Arg-48 mutation inactivates the DNA and DNA.RNA helicase activities and confers a substantial reduction in the incision of UV-damaged DNA suggests a role for these activities in incision. We discuss how RAD3 helicase activities could function in tracking of DNA in search of damage sites and effect enhanced excision repair of actively transcribed genes.
...
PMID:DNA.RNA helicase activity of RAD3 protein of Saccharomyces cerevisiae. 171 38

The human p68 protein, an SV40 large T related antigen, is an RNA dependent ATPase and RNA helicase. It belongs to a new large and highly conserved gene family, the DEAD box proteins, whose members are involved in a variety of processes requiring manipulation of RNA secondary structure such as translation and splicing. Multiple DEAD box genes are present in S.cerevisiae, but only one has previously been described in E.coli. Low stringency screening of an E.coli genomic library with a p68 cDNA probe led to the identification of dbpA, a new E.coli DEAD box gene located at 29.6 minutes on the W3110 chromosome. We report here the nucleotide and deduced amino acid sequences of the gene. We have overexpressed dbpA from its own promoter on a high copy number plasmid and identified the gene product as a approximately 50 kD protein by immunoblotting with an anti-DEAD antibody.
...
PMID:Identification of a putative RNA helicase in E.coli. 221 14

Large T antigen, the regulatory protein encoded by simian virus 40, has DNA helicase activity and unwinds double-stranded DNA at the expense of ATP. T antigen also functions as an RNA helicase separating duplex regions in partially double-stranded RNA substrates. Surprisingly, T antigen RNA helicase activity requires UTP, CTP, or GTP as a cofactor, whereas ATP is an inefficient energy source for the RNA unwinding reaction. Accordingly, T antigen has both an intrinsic non-ATP NTPase activity that is stimulated by single-stranded RNA and an ATPase activity stimulated by single-stranded DNA. Thus, it appears that the bound nucleotide determines whether T antigen acts as an RNA helicase or as a DNA helicase.
...
PMID:RNA unwinding activity of SV40 large T antigen. 247 17

The genome of the hepatitis C virus directs the synthesis of a single polyprotein, which is proteolytically cleaved into at least nine functional proteins. The amino-terminal portion of the polyprotein forms the structural proteins, while the carboxy-terminal region constitutes a variety of viral enzymes. The nonstructural 3 (NS3) protein, consisting of amino acids 1027-1657 of the polyprotein, is believed to be a multifunctional protein with an amino-terminal serine protease domain, which is involved in polyprotein processing, and a carboxy-terminal ATPase/RNA helicase domain, presumably involved in viral replication. We have assembled an expression vector which directs the synthesis of residues 1207-1612 of the polyprotein with an amino-terminal polyhistidine purification tag. This portion of the NS3 protein contains the putative ATPase/helicase domain. The protein has been purified to yield 30-50 mg of enzymatically active protein per liter of culture. The purified NS3 protein has both NTPase and RNA helicase activities. ATP is the preferred substrate for the NTPase; GTP is also utilized; however, UTP is a very poor substrate and CTP is not utilized. The RNA helicase activity is dependent on ATP and divalent cation. Either manganese or magnesium can serve as the divalent cation.
...
PMID:Expression, isolation, and characterization of the hepatitis C virus ATPase/RNA helicase. 748 72


1 2 3 4 5 6 7 8 9 10 Next >>

---