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:2.1.1.37 (DNA methyltransferase)
4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two restriction-modification systems, S1 and S2, are present in Staphylococcus aureus RN450 (S. Iordanescu and M. Surdeanu, J. Gen. Microbiol., 96:277-281, 1976). System S2 affects phage multiplication after both infection and transfection. Unmodified plasmid and chromosomal DNAs are also not expressed following transduction and transformation into a restrictive host. Restricted phages are, however, capable of conferring phage-mediated competence, although the state of competence does not affect the restriction-modification system. The restricting activity of system S2 is inactivated by heat treatment of the cells. An enzymatic activity that restricts unmodified phage DNA in the presence of ATP, Mg2+, and S-adenosylmethionine was recovered from cell-free extracts of a strain RN450 derivative.
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PMID:Biological characteristics of a type I restriction-modification system in Staphylococcus aureus. 14 65

A type II restriction endonuclease (endo R . Bsp) has been purified from Bacillus sphaericus to electrophoretic homogeneity. The enzyme appears to be a single polypeptide chain with a molecular weight of 35000. Its pH optimum is around 8.2, it requires 20 mM Mg2+ for optimal activity and it is inhibited by Zn2+. The yield of the enzyme is higher than that of any type II restriction endonuclease so far reported. The enzyme also cleaves single-stranded DNA, albeit at a slower rate. It seems likely that single-stranded DNA is cleaved at the same sequences as double-stranded DNA. Bacillus sphaericus also contains a modification methylase (meth M . Bsp) which completely protects the cell's own DNA against cleavage by its restriction endonuclease. The methylase activity has been partially purified, it copurifies with the nuclease until the next to the last step. The enzyme does not require ATP or Mg2+, it transfers the methyl group of S-adenosyl-methionine to cytosine residues of DNA. As the action of this methylase completely protects any DNA from endo R . Bsp cleavage, it seems likely that the methylase recognizes and methylates the same sequence (dG-dG-dC-dC) as the nuclease.
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PMID:Biochemical characterization of the restriction-modification system of Bacillus sphaericus. 71 Apr 8

The Escherichia coli plasmid pDXX1 codes for a new restriction-modification system. The specific restriction endonuclease coded by this system has been purified by a procedure that includes phosphocellulose and heparin-agarose chromatography. Sedimentation on glycerol gradients showed one peak of activity with a value of about 12 S. The highly purified enzyme require ATP and Mg2+ for activity as well as S-adenosylmethionine, although some S-adenosylmethionine molecules are probably bound to the enzyme. The enzyme does not cleave lambda DNA at well-defined sites and has a strong non-modified DNA-dependent ATPase activity. The enzyme has also methylase activity acting against non-modified DNA.
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PMID:The EcoDXX1 restriction and modification system of Escherichia coli ET7. Purification, subunit structure and properties of the restriction endonuclease. 299 88

The EcoA restriction enzyme from Escherichia coli 15T- has been isolated. It proves to be an unusual enzyme, clearly related functionally to the classical type I restriction enzymes. The basic enzyme is a two subunit modification methylase. Another protein species can be purified which by itself has no enzymatic activities but which converts the modification methylase to an ATP and S-adenosylmethionine-dependent restriction endonuclease. The DNA recognition sequence of EcoA has an overall structure that is very similar to previously determined type I sequences. It is: 5'-GAGNNNNNNNGTCA-3' 3'-CTCNNNNNNNCAGT-5' where N can be any nucleotide. Modification methylates the adenosyl residue in the specific trinucleotide and the adenosyl residue in the lower strand of the specific tetranucleotide.
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PMID:The EcoA restriction and modification system of Escherichia coli 15T-: enzyme structure and DNA recognition sequence. 632 76

The DNA-binding properties of the EcoP15I DNA methyltransferase (M.EcoP15I; MTase) were studied using electrophoretic mobility shift assays. We show by molecular size-exclusion chromatography and dimethyl suberimidate cross-linking that M.EcoP15I is a dimer in solution. While M.EcoP15I binds approx. threefold more tightly to its recognition sequence, 5'-CAGCAG-3', than to non-specific sequences in the presence of AdoMet or its analogs, the discrimination between specific and non-specific sequences significantly increases in presence of ATP. These results suggest for the first time a role for ATP in DNA recognition by type-III restriction-modification enzymes. Furthermore, we show that although c2 EcoPI mutant MTases are defective in AdoMet binding, they are still able to bind DNA in a sequence-specific manner.
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PMID:DNA recognition by the EcoP15I and EcoPI modification methyltransferases. 760 79

A specific mechanism was given for ethionine-induced alpha-fetoprotein gene activity and is as follows: 1. Ethionine acts on competent cell types (e.g. stem cells) having one alpha-fetoprotein-enhancer-albumin gene region that is active and possesses embryonic-like low levels of S-adenosyl-L-methionine synthesis: DNA methylase genes for the enhancer regions are in the heterochromatic state. 2. ATP: L-methionine-S-adenosyltransferase acts upon ethionine and ATP to form S-adenosyl-L-ethionine; this lowers the amount of S-adenosyl-L-methionine synthesized and in turn also the synthesis of methyl-nicotinamide; the concentration of nicotinamide increases; there is an inhibition of polyADP ribosylation; hyporibosylation of histone 1 of nucleosomes; deblocking of embryonic type heterochromatin; and finally the second alpha-fetoprotein gene becomes activated. 3. Reversal occurs with the introduction of methionine; increase of S-adenosyl-L-methionine synthesis; increased methylnicotinamide synthesis; increased polyADP-ribose synthesis; ribosylation of H-1 protein to normal levels; and then the packing configuration of chromatin causes rerepression of alpha-fetoprotein genes. It is suggested that ethionine has the ability to perturb a methyl-sensitive heterochromatin that is peculiar to chromatin synthesized during embryogenesis. Therefore such repressed embryonic genes as alpha-fetoprotein are differentially susceptible to low concentrations of active methyl groups. Ethionine causes this hypomethylated heterochromatin by interference with S-adenosyl-L-methionine synthesis.
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PMID:A specific mechanism for ethionine-induced embryonic gene activity. 768 49

EcoP15I DNA methyltransferase (Mtase) recognizes the asymmeteric sequence CAGCAG and catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to the second adenine residue. We have investigated the DNA binding properties of EcoP15I DNA Mtase using gel mobility shift assays. EcoP15I DNA Mtase binds approximately threefold more tightly to DNA containing its recognition sequence, CAGCAG, than to non-specific sequences in the absence or presence of cofactors. Interestingly, in the presence of ATP the discrimination between specific and non-specific sequences increases significantly. These results suggest for the first time a role for ATP in DNA recognition by type III restriction-modification enzymes. In addition, we have shown that bromodeoxyuridine-containing oligonucleotides form complexes with EcoP15I DNA Mtase that are crosslinked upon irradiation. More importantly, we have shown that the crosslink site is at the site of DNA binding, since it can be suppressed by an excess of unmodified oligonucleotide. EcoP15I DNA Mtase exhibited Michaelis-Menten kinetics with both unmodified and bromodeoxyuridine-substituted DNA, with a higher specificity constant for the latter. Furthermore, gel mobility shift assays showed that proteolyzed EcoP15I DNA Mtase formed a specific complex with DNA, which had similar mobility as the native protein-DNA complex. Taken together these results form the basis for a detailed structure-function analysis of EcoP15I DNA Mtase.
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PMID:Interaction of EcoP15I DNA methyltransferase with oligonucleotides containing the asymmetric sequence 5'-CAGCAG-3'. 793 97

This report completes a preliminary analysis of the sequence of the 330,740-bp chlorella virus PBCV-1 genome, the largest virus genome to be sequenced to date. The PBCV-1 genome is 57% the size of the genome from the smallest self-replicating organism, Mycoplasma genitalium. Analysis of 74 kb of newly sequenced DNA, from the right terminus of the PBCV-1 genome, revealed 153 open reading frames (ORFs) of 65 codons or longer. Eighty-five of these ORFs, which are evenly distributed on both strands of the DNA, were considered major ORFs. Fifty-nine of the major ORFs were separated by less than 100 bp. The largest intergenic distance was 729 bp, which occurred between two ORFs located in the 2.2-kb inverted terminal repeat region of the PBCV-1 genome. Twenty-seven of the 85 major ORFs resemble proteins in databases, including the large subunit of ribonucleotide diphosphate reductase, ATP-dependent DNA ligase, type II DNA topoisomerase, a helicase, histidine decarboxylase, dCMP deaminase, dUTP pyrophosphatase, proliferating cell nuclear antigen, a transposase, fungal translation elongation factor 3 (EF-3), UDP glucose dehydrogenase, a protein kinase, and an adenine DNA methyltransferase and its corresponding DNA site-specific endonuclease. Seventeen of the 153 ORFs resembled other PBCV-1 ORFs, suggesting that they represent either gene duplications or gene families.
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PMID:Analysis of 74 kb of DNA located at the right end of the 330-kb chlorella virus PBCV-1 genome. 935 47

EcoP1I and EcoP15I are members of type III restriction-modification enzymes. EcoPI and EcoP15I DNA methyltransferases transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the N6 position of the second adenine residues in their recognition sequences, 5'-AGACC-3' and 5'-CAGCAG-3' respectively. We have altered various residues in two highly conserved sequences, FxGxG (motif I) and DPPY (motif IV) in these proteins by site-directed mutagenesis. Using a mixture of in vivo and in vitro assays, our results on the mutational analysis of these methyltransferases demonstrate the universal role of motif I in AdoMet binding and a role for motif IV in catalysis. All six cysteine residues in EcoP15I DNA methyltransferase have been substituted with serine and the role of cysteine residues in EcoP15I DNA methyltransferase catalysed reaction assessed. The Res subunits of type III restriction enzymes share a distant sequence similarity with and contain the motifs characteristic of the DEAD box proteins. We have carried out site-directed mutagenesis of the conserved residues in two of the helicase motifs of the EcoP1I restriction enzyme in order to investigate the role of motifs in DNA cleavage by this enzyme. Our findings indicate that certain conserved residues in these motifs are involved in ATP hydrolysis while the other residues are involved in coupling restriction of DNA to ATP hydrolysis. Taken collectively, these results form the basis for a detailed structure-function analysis of EcoP1I and EcoP15I restriction enzymes.
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PMID:Functional analysis of conserved motifs in type III restriction-modification enzymes. 962 45

Type I DNA restriction enzymes are large, molecular machines possessing DNA methyltransferase, ATPase, DNA translocase and endonuclease activities. The ATPase, DNA translocase and endonuclease activities are specified by the restriction (R) subunit of the enzyme. We demonstrate that the R subunit of the Eco KI type I restriction enzyme comprises several different functional domains. An N-terminal domain contains an amino acid motif identical with that forming the catalytic site in simple restriction endonucleases, and changes within this motif lead to a loss of nuclease activity and abolish the restriction reaction. The central part of the R subunit contains amino acid sequences characteristic of DNA helicases. We demonstrate, using limited proteolysis of this subunit, that the helicase motifs are contained in two domains. Secondary structure prediction of these domains suggests a structure that is the same as the catalytic domains of DNA helicases of known structure. The C-terminal region of the R subunit can be removed by elastase treatment leaving a large fragment, stable in the presence of ATP, which can no longer bind to the other subunits of Eco KI suggesting that this domain is required for protein assembly. Considering these results and previous models of the methyltransferase part of these enzymes, a structural and operational model of a type I DNA restriction enzyme is presented.
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PMID:On the structure and operation of type I DNA restriction enzymes. 1039 Mar 54


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