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)

The nucleotide sequence of the gene coding for the 5'-GGCC and 5'-CCGG specific DNA methyltransferase of the Bacillus subtilis phage SPR was determined by the Maxam-Gilbert procedure. Transcriptional and translational signals of the sequence were assigned with the help of S1 mapping and translation in E. coli minicells. The gene codes for a 49 kd polypeptide. The amino acid sequence of the SPR methylase shows regions of homology with the sequence of the 5'-GGCC-specific BspRI modification methylase.
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PMID:Structure of the gene coding for the sequence-specific DNA-methyltransferase of the B. subtilis phage SPR. 609 17

We have determined the nucleotide sequence of a 4.0-kilobase DNA fragment containing the genes of the PstI restriction-modification system. Two large open reading frames were identified within the sequence and were ascribed to the restriction enzyme and methylase by the analysis of a series of deletion mutants. The two genes are encoded on opposite DNA strands, and hence must be transcribed from separate promoters rather than as a polycistronic message. The sequence of the first 10 amino acids of the restriction endonuclease was determined by sequential Edman degradation of the purified protein, permitting the alignment of the polypeptide with the DNA sequence. The NH2 terminus of the modification enzyme was established by sequential Edman degradation of the protein synthesized in bacterial minicells with different radiolabeled amino acids. The initiation codons of the two genes are separated by 130 base pairs. The deduced amino acid sequences indicate that the restriction endonuclease contains 326 amino acids with a calculated Mr = 37,370; the modification enzyme is composed of 507 amino acids with a calculated Mr = 56,830. There is no significant homology between the two proteins at the level of the primary structure. Antibody raised against the purified restriction endonuclease did not immunoprecipitate the modification enzyme. The transcription initiation sites were mapped using mung bean nuclease. Both of the transcripts begin with adenosine. The initiation sites are separated by only 70 base pairs. This close proximity suggests that the promoters for the two divergent genes overlap. DNase I protection experiments show that Escherichia coli RNA polymerase has a higher affinity for the methylase promoter than for the restriction enzyme promoter.
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PMID:The organization and complete nucleotide sequence of the PstI restriction-modification system. 633 92

A DNA methylase was purified in a homogeneous state from a extremely thermophilic bacterium, Thermus thermophilus HB8, by chromatography on, successively, phosphocellulose, CM-cellulose, and heparin-Sepharose. The molecular weight of the enzyme was determined to be about 44,000 by gel filtration on a Sephadex G-100 column and 41,000 by SDS-poly-acrylamide gel electrophoresis, and these findings suggest a single polypeptide enzyme. The enzyme develops maximum activity around pH 7.4 and at 70 degrees C. Enzymatic activity is completely inhibited by 0.2 M NaCl or 2 mM HgCl2. The enzyme transfers methyl groups from S-adenosyl-L-methionine to a double stranded DNA. The sole product of the reaction was identified as N-6-methyl adenine after hydrolysis of the DNA with formic acid. The enzyme kinetics obey the Michaelis-Menten equation and Km values for S-adenosylmethionine and lambda phage DNA were determined to be 0.8 muM and 10 microgram/ml, respectively. The enzyme does not transfer methyl groups to TthHB8I endonuclease digested DNA as well as the host (T. thermophilus HB8) DNA. The number of methyl groups of the fully methylated phiX174 RF DNA was about twice as many as TthHB8I endonuclease sites on the DNA. The distribution of the methyl groups of phiX174 RF DNA among the HaeIII fragments was the same as that of TthHB8I endonuclease sites, suggesting that this DNA methylase is the other component of the modification-restriction system including TthHB8I endonuclease. The enzyme probably recognizes the sequence, 5'-TCGA-3', in a double stranded DNA and probably methylates adenine in the above sequence.
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PMID:A DNA methylase from Thermus thermophilus HB8. 644 53

A gene encoding a DNA invertase-like enzyme was identified adjacent to the PaeR7I restriction-modification system (R-M), and was named paeR7IN (N for iNvertase). Sequence analysis revealed that this gene has the same polarity as the PaeR7IRM operon, and would encode a polypeptide of 21,506 Da. An amino-acid sequence similarity of 45-49% was found between the deduced protein product and various DNA invertases.
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PMID:Identification of a gene encoding a DNA invertase-like enzyme adjacent to the PaeR7I restriction-modification system. 760 31

Cytosine methylation within DNA has been implicated in genetic imprinting, X-chromosome inactivation, regulation of tissue-specific gene expression, aging, and cancer. Unfortunately, DNA (cytosine-5)-methyltransferases (EC 2.1.1.37) from various mammalian sources have been difficult to isolate and stabilize, precluding investigations of these critical enzymes. We describe a novel FPLC purification of the 190,000 Mr DNA methyltransferase from mouse Friend erythroleukemia cells. The homogeneous 190 kD Mr form of the enzyme is the only polypeptide detected at various stages of cell growth and has not undergone detectable N-terminal proteolysis.
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PMID:Purification and stabilization of mouse DNA methyltransferase. 786 41

The Thermus aquaticus DNA methyltransferase M.Taq I (EC 2.1.1.72) methylates N6 of adenine in the specific double-helical DNA sequence TCGA by transfer of --CH3 from the cofactor S-adenosyl-L-methionine. The x-ray crystal structure at 2.4-A resolution of this enzyme in complex with S-adenosylmethionine shows alpha/beta folding of the polypeptide into two domains of about equal size. They are arranged in the form of a C with a wide cleft suitable to accommodate the DNA substrate. The N-terminal domain is dominated by a nine-stranded beta-sheet; it contains the two conserved segments typical for N-methyltransferases which form a pocket for cofactor binding. The C-terminal domain is formed by four small beta-sheets and alpha-helices. The three-dimensional folding of M.Taq I is similar to that of the cytosine-specific Hha I methyltransferase, where the large beta-sheet in the N-terminal domain contains all conserved segments and the enzymatically functional parts, and the smaller C-terminal domain is less structured.
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PMID:Three-dimensional structure of the adenine-specific DNA methyltransferase M.Taq I in complex with the cofactor S-adenosylmethionine. 797 91

The murine C-5 cytosine DNA methyltransferase (MTase, E.C.2.1.1.37) containing a hexahistidine affinity leader peptide has been expressed at levels which are at least 50-fold higher than previously reported. The recombinant enzyme has activity levels similar to the wild-type enzyme. The recombinant polypeptide binds to and elutes from a nickel affinity resin (IMAC resin). No dramatic differences in post-translational modification between the wild-type and recombinant enzyme were observed. The recombinant system will be useful in performing site-directed mutagenesis and will facilitate enzymological and biological investigations of this enzyme.
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PMID:Baculovirus-mediated high level expression of a mammalian DNA methyltransferase. 798 May 70

Three regions of sequence similarity have been reported in several protein and small-molecule S-adenosylmethionine-dependent methyltransferases. Using multiple alignments, we have now identified these three regions in a much broader group of methyltransferases and have used these data to define a consensus for each region. Of the 84 non-DNA methyltransferase sequences in the GenBank, NBRF PIR, and Swissprot databases comprising 37 distinct enzymes, we have found 69 sequences possessing motif I. This motif is similar to a conserved region previously described in DNA adenine and cytosine methyltransferases. Motif II is found in 46 sequences, while motif III is found in 61 sequences. All three regions are found in 45 of these enzymes, and an additional 15 have motifs I and III. The motifs are always found in the same order on the polypeptide chain and are separated by comparable intervals. We suggest that these conserved regions contribute to the binding of the substrate S-adenosylmethionine and/or the product S-adenosylhomocysteine. These motifs can also be identified in certain nonmethyltransferases that utilize either S-adenosylmethionine or S-adenosylhomocysteine, including S-adenosylmethionine decarboxylase, S-adenosylmethionine synthetase, and S-adenosylhomocysteine hydrolase. In the latter two types of enzymes, motif I is similar to the conserved nucleotide binding motif of protein kinases and other nucleotide binding proteins. These motifs may be of use in predicting methyltransferases and related enzymes from the open reading frames generated by genomic sequencing projects.
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PMID:Widespread occurrence of three sequence motifs in diverse S-adenosylmethionine-dependent methyltransferases suggests a common structure for these enzymes. 817 27

The ALLI gene, located at chromosome band 11q23, is involved in acute leukemia through a series of chromosome translocations and fusion to a variety of genes, most frequently to A4 and AF9. The fused genes encode chimeric proteins proteins. Because the Drosophila homologue of ALL1, trithorax, is a positive regulator of homeotic genes and acts at the level of transcription, it is conceivable that alterations in ALL1 transcriptional activity may underlie its action in malignant transformation. To begin studying this, we examined the All1, AF4, AF9, and AF17 proteins for the presence of potential transcriptional regulatory domains. This was done by fusing regions of the proteins to the yeast GAL4 DNA binding domain and assaying their effect on transcription of a reporter gene. A domain of 55 residues positioned at amino acids 2829-2883 of ALL1 was identified as a very strong activator. Further analysis of this domain by in vitro mutagenesis pointed to a core of hydrophobic and acidic residues as critical for the activity. An ALL1 domain that repressed transcription of the reporter gene coincided with the sequence homologous to a segment of DNA methyltransferase. An AF4 polypeptide containing residues 480-560 showed strong activation potential. The C-terminal segment of AF9 spanning amino acids 478-568 transactivated transcription of the reporter gene in HeLa but not in NIH 3T3 cells. These results suggest that ALL1, AF4, and probably AF9 interact with the transcriptional machinery of the cell.
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PMID:Domains with transcriptional regulatory activity within the ALL1 and AF4 proteins involved in acute leukemia. 861 64

Cytosine (C-5)-specific DNA methyltransferases share a set of ten conserved motifs distributed evenly throughout the entire polypeptide chain. The first conserved motif contains a Phe, which is intimately associated with cofactor recognition. In the pseudo-DNA methyltransferase M.SpoI, encoded by the pmt1 gene in Schizosaccharomyces pombe, a Tyr replaces this Phe residue. We describe the properties of a mutant form of M.MspI, a typical cytosine (C-5)-specific DNA methyltransferase, in which Tyr replaces the conserved Phe. This mutant shows differences in ternary complex formation and in the pattern of covalent complex formation with an inhibitory, fluorinated DNA duplex which may be due to anomalous hydrogen bonding between the mutant Tyr hydroxyl group and the catalytic loop of the enzyme or through interference with cofactor binding.
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PMID:Substitution of the conserved phenylalanine in the S-adenosyl-L-methionine binding site of M.MspI with tyrosine modifies the kinetic properties of the enzyme. 962 62


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