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

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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)

Both exponentially growing and serum-arrested subcloned CV-1 cell cultures were infected with simian virus 40 (SV40). By 24 h after infection 96% of the nuclei of these permissive cells contained SV40 T-antigen. Analysis of the average DNA content per cell at various times after infection indicated that by 24 h most of the cells contained amounts of DNA similar to those normally found in G(2) cells. Analysis of cell cycle distributions indicated that a G(2) DNA complement was maintained by over 90% of the cells in the infected populations 24 to 48 h postinfection. Cells continued to synthesize SV40 DNA during the first 50 h after infection, and cytopathic effect was first observed 60 h after inoculation. After infection the number of mitotic cells that could be recovered by selective detachment decreased precipitously and was drastically reduced by 24 h. A study of the kinetics of decline in the number of mitotic cells suggests that this decline is related to an event during the cell cycle at or near the G(1)-S-phase border upon which commencement of SV40 DNA replication apparently depends. It was concluded that after SV40 infection, stationary cells are induced to cycle, and cycling cells complete one round of cellular DNA synthesis but do not divide. Although the infected cells continue to synthesize viral DNA, they do not appear able to reinitiate cellular DNA replication units. These results imply that the abundance of T-antigen (produced independently of cell cycle phase) in the presence of the enzymes required for continued DNA synthesis is not sufficient for reinitiation of cellular DNA synthesis.
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PMID:Simian virus 40-host cell interaction during lytic infection. 22 30

We propose that the UGA terminator regularly occurs as a tryptophan codon in yeast mitochondrial DNA. This conclusion is based on the sequence analysis of mitochondrial DNA regions coding for structural genes of cytochrome b, cytochrome oxidase, and the ATPase.
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PMID:Use of the UGA terminator as a tryptophan codon in yeast mitochondria. 22 81

We have isolated a new DNA-dependent ATPase from E. coli. The enzyme has been purified to greater than 90% purity. It appears to be composed of two identical polypeptide chains of molecular weight 20,000. The enzyme catalyzed the hydrolysis of ATP in the presence, but not in the absence, of single-stranded DNA. Double-stranded DNA is not a cofactor. The products of hydrolysis are ADP and Pi. The enzyme also catalyzed strand separation of duplex DNA in the presence of ATP and E. coli DNA binding protein. Two E. coli proteins capable of promoting strand separation have been reported previously and have been termed helicase I and II (Abdel-Monem, M., and Hoffmann-Berling, H. (1977) Eur. J. Biochem. 79, 33-38). Accordingly, this protein is named helicase III.
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PMID:Enzyme-catalyzed DNA unwinding. A DNA-dependent ATPase from E. coli. 22 86

A protein isolated from Escherichia coli complements the DNA gyrase A (NalA) protein to generate an activity that relaxes supercoiled DNA. Oxolinic acid, a known inhibitor of DNA gyrase, blocks this activity and causes double-strand cleavage of DNA at the same sites as are attacked by DNA gyrase. The protein, of molecular weight 50,000, appears to be fragment of the DNA gyrase B (Cou) protein (molecular weight, 90,000) as judged by the identical sizes of numerous peptides produced by partial proteolytic digestion. The complex of this fragment and the gyrase A protein lacks both the DNA-supercoiling and DNA-dependent ATPase activities of DNA gyrase.
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PMID:DNA gyrase: purification and catalytic properties of a fragment of gyrase B protein. 23 May 5

A method was devised for isolation of large numbers of energy-transducing ATPase (coupling factor) mutants based on a modification of the procedure of Hong and Ames (Hong, J. and Ames, B. N. (1971) Proc. Natl. Acad. Sci. U.S. 68, 3158-3162) for localized mutagenesis of any small region of the bacterial chromosome using transducing phages. The principle of this procedure is to mutate P1-transducing phage particles carrying the ATPase genes (Unc (uncoupled) DNA) using the strong chemical mutagen hydroxylamine. By transducing ilv- auxotrophs, a marker closely linked to Unc, to prototrophs, mutated Unc DNA can be introduced into the chromosome. We have used this method in conjunction with suitable selection procedures to isolate about 90 Unc- strains which have been classified by physiological, genetic, and biochemical criteria into three different phenotypes (Unc A, B, D). Mutants of the Unc D phenotype which were studied in detail were found to have the following properties: (1) aerobic growth yields on glucose are considerably lower than the wild type; growth occurs on glucose under anaerobic conditions; (2) Unc D lesions map near the ilv operon; (3) O2 uptake is comparable to the rate of wild type; (4) vesicles catalyze respiratory-dependent transhydrogenation, but show very low levels of Ca2+ ATP-dependent transhydrogenation; Mg2+ is ineffective; (5) oxidative phosphorylation is almost completely blocked irrespective of which metal ion is used; (6) the specific activity of ATPase is only about 20% of the wild type: (7) purified ATPase was found to have a marked specificity for Ca2+ as a divalent metal for ATP hydrolysis. A summary of properties of the new Unc mutants is discussed.
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PMID:Isolation and properties of Escherichia coli ATPase mutants with altered divalent metal specificity for ATP hydrolysis. 24 Apr 43

Two active components alpha and beta of micrococcus luteus DNA gyrase, of peptide weights of 115,000 and 97,000, respectively, have been purified. Each individual component exhibits little DNA gyrase activity; the ATP-dependent negative supercoiling of a covalently closed circular DNA duplex is catalyzed by a combination of the two. Covalent closure by Escherichia coli ligase of a circular DNA containing single-chain scissions, when carried out in the presence of a combination of the DNA gyrase components alpha and beta, gives a positively supercoiled DNA upon removal of the bound protein molecules. ATP was not present during the ligase treatment; therefore the positive supercoiling of DNA observed is a result of the binding of gyrase molecules, presumably as multi-subunit oligomers, during the ligation step. This is in contrast to the negative supercoiling of DNA catalyzed by gyrase in the presence of ATP. A model in which negative supercoiling of DNA is achieved by ATP-modulated repetitive wrapping of the DNA around gyrase is described. The model also suggests a plausible mode of action by which translocation of a DNA along its helix axis can be actively driven by an ATPase.
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PMID:Micrococcus luteus DNA gyrase: active components and a model for its supercoiling of DNA. 27 55

Antischizophrenic agents, phenothiazine and nonphenothiazine, inhibit the transformation of the T-lymphocyte in vitro. This inhibition occurs only in the early event and is neither competitive with dopamine, nor appears to involve Na+/K+ adenosine triphosphatase. RNA synthesis is more sensitive to the inhibitory effect than DNA or protein synthesis. This leads to the conclusion that chlorpromazine may act by inhibiting the synthesis of newly formed RNA, and subsequently, transformation, rather than by alteration of the cell membrane.
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PMID:Effect of psychotropic agents upon the blastogenic response of human t-lymphocytes. 30 Jun 33

Rhodamine 6G was found to be a specific inhibitor of aerobic growth of yeast, having no effect on fermentative growth. A single step spontaneous mutant of S. cerevisiae resistant to rhodamine 6G was isolated, which showed cross-resistance to the ATPase inhibitors venturicidin and triethyltin, to the uncoupler 1799, to bongkrekic acid and to cycloheximide, but not to oligomycin or to the inhibitors of mito chondrial protein synthesis, chloramphenicol and erythromycin. The genetic analysis of this mutant showed that both nuclear and cytoplasmic (but apparently not mitochondrial) factors may be involved in the determination of the mutation. The behaviour is discussed as a possible function for 2 micron circular (omicron) DNA.
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PMID:Extra-chromosomal inheritance of rhodamine 6G resistance in Saccharomyces cerevisiae. 32 67

Extracts of the DNA initiation-defective mutant Escherichia coli dnaB252 are inactive in a dnaB complementation assay but yield a ribonucleoside triphosphatase activity of native molecular weight of about 270,000 (60,000-dalton polypeptide as subunit) that can be inactivated by antibody to dnaB. On the other hand, extracts of a dnaB252(P1 bac) lysogen, in which the dnaB mutation is suppressed in vivo by the constitutive expression of the P1 dnaB analog (ban protein), are active in dnaB complementation and the activity is also sensitive to dnaB antibody. Upon further purification two proteins (with polypeptide molecular weights of 60,000 and 56,000, respectively) are found associated with each other (native molecular weight about 270,000). The larger and the smaller protein are tentatively identified as the dnaB and P1 ban protein. It is suggested that suppression of the dnaB mutation by prophage P1 bac is accomplished by a stabilization of dnaB252 by P1 ban subunit molecules in a heteromultimer.
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PMID:Escherichia coli dnaB mutant defective in DNA initiation: isolation and properties of the dnaB protein. 34 77

Escherichia coli DNA gyrase catalyzes negative supercoiling of closed duplex DNA at the expense of ATP. Two additional activities of the enzyme that have illuminated the energy coupling component of the supercoiling reaction are the DNA-dependent hydrolysis of ATP to ADP and P(i) and the alteration by ATP of the DNA site specificity of the gyrase cleavage reaction. This cleavage of both DNA strands results from treatment with sodium dodecyl sulfate of the stable gyrase-DNA complex that is trapped by the inhibitor oxolinic acid. Either ATP or a nonhydrolyzable analogue, adenyl-5'-yl-imidodiphosphate (App[NH]p), shifts the primary cleavage site on ColE1 DNA. The prevention by novobiocin and coumermycin A(1) of this cleavage rearrangement places the site of action of the antibiotics at a reaction step prior to ATP hydrolysis. The step blocked is the binding of ATP because coumermycin A(1) and novobiocin interact competitively with ATP in the ATPase and supercoiling assays; the K(i) values are more than four orders of magnitude less than the K(m) for ATP. This simple mechanism accounts for all effects of the drugs on DNA gyrase. Studies with App[NH]p, another potent competitive inhibitor of reactions catalyzed by gyrase, show that cleavage of a high energy bond is not required for driving DNA into the higher energy supercoiled form. With substrate levels of gyrase, App[NH]p induces supercoiling that is proportional to the amount of enzyme; a -0.3 superhelical turn was introduced per gyrase protomer A. We postulate that ATP and App[NH]p are allosteric effectors of a conformational change of gyrase that leads to one round of supercoiling. Nucleotide dissociation favored by hydrolysis of ATP returns gyrase to its original conformation and thereby permits enzyme turnover. Such cyclic conformational changes accompanying alteration in nucleotide affinity also seem to be a common feature of energy transduction in other diverse processes including muscle contraction, protein synthesis, and oxidative phosphorylation.
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PMID:Energy coupling in DNA gyrase and the mechanism of action of novobiocin. 36 1


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