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 genes coding for the class-II Serratia marcescens restriction-modification system have been cloned and expressed in E. coli. Recombinant clones, restricted incoming phage only poorly; the recombinant plasmids, however, became fully modified in vivo, i.e. completely resistant against digestion with R.SmaI. The determined nucleotide sequence of the cloned system revealed three open reading frames with lengths of 252 bp, 741 bp, and 876 bp. Through various deletion experiments and an insertion-mutation experiment the 876 bp open reading frame could be assigned to the SmaI DNA modification enzyme and the 741 bp open reading frame to the SmaI restriction endonuclease. Mapping of the transcription start sites of the genes revealed that the SmaI endonuclease is transcribed as polycistronic mRNA together with a 252 bp long preceding open reading frame of unknown function. No homology was found when comparing the amino acid sequence of M.SmaI with the published sequences of m5C-specific DNA modification methyltransferases. On the other hand, a stretch of 14 amino acids in the C-proximal region of M.SmaI shows a significant homology to the C-proximal amino acid sequences of the N6A-methyltransferases M.HinfI and M.DpnIIA and the N4C-methyltransferase M.PvuII.
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PMID:Cloning, characterization and heterologous expression of the SmaI restriction-modification system. 269 8

The ability of Legionella pneumophila to act as a recipient of IncP and IncQ plasmids in matings with Escherichia coli varies widely from strain to strain. We found that the low efficiency of mating of the Philadelphia-1 strain is due to a type II restriction-modification system, and we isolated and characterized a Philadelphia-1 mutant that lacks the restriction enzyme activity.
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PMID:Isolation of a Legionella pneumophila restriction mutant with increased ability to act as a recipient in heterospecific matings. 270 72

The DdeI restriction-modification system was previously cloned and has been maintained in E. coli on two separate and compatible plasmids (1). The nucleotide sequence of the endonuclease and methylase genes has now been determined; it predicts proteins of 240 amino acids, Mr = 27,808, and 415 amino acids, Mr = 47,081, respectively. Inspection of the DNA sequence shows that the 3' end of the methylase gene had been deleted during cloning. The clone containing the complete methylase gene was made and compared to that containing the truncated gene; only clones containing the truncated form support the endonuclease gene in E. coli. Bal-31 deletion studies show that methylase expression in the Dde clones is also dependent upon orientation of the gene with respect to pBR322. The truncated and complete forms of the methylase protein were purified and compared; the truncated form appears to be more stable and active in vitro. Finally, comparison of the deduced amino acid sequence of M. DdeI with that of other known cytosine methylases shows significant regions of homology.
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PMID:Nucleotide sequence of the DdeI restriction-modification system and characterization of the methylase protein. 282 26

The complete type II restriction-modification system of Salmonella infantis was cloned in Escherichia coli as an R . Sau3AI fragment of 3,430 base pairs. The clone was shown to express the restriction endonuclease as well as the modification methylase. The nucleotide sequence of the above fragment showed two open reading frames of 461 and 230 codons in tail-to-tail orientation. These were shown to represent the modification methylase M . SinI and the restriction endonuclease R . SinI, respectively. The methylase M . SinI amino acid sequence revealed a considerable similarity to those of other deoxycytidylate methylases. In contrast, endonuclease R . SinI did not exhibit such a similarity to other restriction enzymes.
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PMID:Cloning and complete nucleotide sequences of the type II restriction-modification genes of Salmonella infantis. 283 59

To study the factors essential for a functional restriction system, the PaeR7 restriction-modification system has been introduced and expressed in murine cells. Transfer of this system was accomplished in two steps. First, cells containing sufficient PaeR7 methylase to completely methylate the mouse genome were constructed. In the second step, the mouse metallothionein promoter-regulated, endonuclease expression vector linked to the hygromycin B resistance selection marker was used to transfect the high methylase-expressing cells. Sixty percent of the clones isolated contained PaeR7 endonuclease enzymatic activity. Transfected cells expressing both methylase and endonuclease were incapable of blocking infection by DNA viruses, and possible explanations are discussed.
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PMID:Introduction and expression of the bacterial PaeR7 restriction endonuclease gene in mouse cells containing the PaeR7 methylase. 285 May 39

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 genes of the 5'-GGCC specific BsuRI restriction-modification system of Bacillus subtilis have been cloned and expressed in E. coli and their nucleotide sequence has been determined. The restriction and modification genes code for polypeptides with calculated molecular weights of 66,314 and 49,642, respectively. Both enzymes are coded by the same DNA strand. The restriction gene is upstream of the methylase gene and the coding regions are separated by 780 bp. Analysis of the RNA transcripts by S1-nuclease mapping indicates that the restriction and modification genes are transcribed from different promoters. Comparison of the amino acid sequences revealed no homology between the BsuRI restriction and modification enzymes. There are, however, regions of homology between the BsuRI methylase and two other GGCC specific modification enzymes, the BspRI and SPR methylases.
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PMID:Nucleotide sequence of the BsuRI restriction-modification system. 299 8

Several restriction systems were detected in different strains of Streptomyces antibioticus by using actinophages as biological indicators. Adsorption of phages to the bacteria, together with the study of the efficiency of plating gave an initial indication of restriction in three strains. The alternation of efficiency of plating values obtained from restricting and nonrestricting hosts, gave evidence for the presence of a restriction-modification system in another strain. No common modification systems were detected among the different strains tested. Two specific endonucleases with a possible role in restriction were detected in strains ATCC 11891 and ETH 7451, respectively.
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PMID:Restriction-modification systems in Streptomyces antibioticus. 299 80

Mycoplasma bacteriophage L51 single-stranded DNA and L2 double-stranded DNA are host cell modified and restricted when they transfect Acholeplasma laidlawii JA1 and K2 cells. The L51 genome has a single restriction endonuclease MboI site (recognition sequence GATC), which contains 5-methylcytosine when the DNA is isolated from L51 phage grown in K2 cells but is unmethylated when the DNA is from phage grown in JA1 cells. This GATC sequence is nonessential, since an L51 mutant in which the MboI site was deleted was still viable. DNA from this deletion mutant phage was not restricted during transfection of either strain K2 or JA1. Therefore, strain K2 restricts DNA containing the sequence GATC, and strain JA1 restricts DNA containing the sequence GAT 5-methylcytosine. We conclude that K2 cells have a restriction system specific for DNA containing the sequence GATC and protect their DNA by methylating cytosine in this sequence. In contrast, JA1 cells (which contain no methylated DNA bases) have a newly discovered type of restriction-modification system. From results of studies of the restriction of specifically methylated DNAs, we conclude that JA1 cells restrict DNA containing 5-methylcytosine, regardless of the nucleotide sequence containing 5-methylcytosine. This is the first report of a DNA restriction activity specific for a single (methylated) base. Modification in this system is the absence of cytosine methylating activity. A restriction-deficient variant of strain JA1, which retains the JA1 modification phenotype, was isolated, indicating that JA1 cells have a gene product with restriction specificity for DNA containing 5-methylcytosine.
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PMID:Mycoplasma restriction: identification of a new type of restriction specificity for DNA containing 5-methylcytosine. 300 Oct 23

Bal31 deletion experiments on clones of the PaeR7 restriction-modification system from Pseudomonas aeruginosa demonstrate that it is arranged as an operon, with the methylase gene preceding the endonuclease gene. The DNA sequence of this operon agrees with in vitro transcription-translation assays which predict proteins of 532 amino acids, Mr = 59,260 daltons, and 246 amino acids, Mr = 27,280 daltons, coincident with the methylase and endonuclease genes, respectively. These predicted values coincide with the measured molecular weights of the purified, denatured PaeR7 endonuclease and methylase proteins. The first twenty amino acids from the amino-terminus of the purified endonuclease exactly match those predicted from the DNA sequence. Finally, potential regulatory mechanisms for the expression of phage restriction are described based on the properties of several PaeR7 subclones.
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PMID:Nucleotide sequence of the PaeR7 restriction/modification system and partial characterization of its protein products. 300 39


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