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 for restriction-modification system EcoRII have been cloned from plasmid N3 DNA using RSF2124 as a vector plasmid. The hybrid plasmids designated pFK321 and pFK322 contained a 5.8 megadaltons EcoRI--fragment derived from N3 DNA including the genes for restriction-modification system EcoRII and a gene for resistance to sulfanilamide.
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PMID:Molecular cloning of EcoRII endonuclease and methylase genes. 624 37

The Eco RI endonuclease and methylase recognize the same hexanucleotide substrate sequence. We have determined the sequence of a fragment of DNA which encodes these enzymes using the chain-termination method of Sanger (Sanger, F., Nicklen, S., and Coulson, A. R. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5463-5467). The amino acid sequences of both enzymes were derived from the DNA sequence. The coding regions selected include the only open translational frames of sufficient length to accommodate the enzymes. They coincide with previously established gene boundaries and orientation. The predicted amino acid sequences correlate well with analyses of the purified protein. Comparison of the nucleotide and protein sequences reveals no homology between the endonuclease and methylase which might provide insight into the origin of the restriction-modification system or the mechanism of common substrate recognition. Based on secondary structure predictions, the two enzymes also have grossly different molecular architecture. The base composition of the sequence is 65% A + T, and the codon usage is significantly different from that observed in several Escherichia coli chromosomal genes. In some cases, frequently selected codons are recognized by minor tRNA species. A spontaneous mutation in the endonuclease gene was isolated. Serine replaces arginine at residue 187. In crude extracts, Eco RI specific cleavage is approximately 0.3% wild type.
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PMID:Sequence analysis of the DNA encoding the Eco RI endonuclease and methylase. 625 3

A library of Bacillus subtilis chromosomal deoxyribonucleic acid (DNA) was constructed, using lambda charon 4A as a cloning vector. Partially cleaved Bacillus subtilis DNA was prepared by partial methylation with EcoRI methylase, followed by complete EcoRI endonuclease digestion. More than 95% of the phage particles carried B. subtilis DNA inserts. When this library was screened for transforming activity, using competent cells, 70% of the genetic markers tested were found in a sample of 1,710 plaques. Cloned genetic loci were found to be about 100-fold more efficient in transforming activity than chromosomal DNA. Intact phage particles containing the pheA locus were found to be able to transform competent recipients with approximately the same efficiency as phage DNA. Transformation by intact particles was insensitive to deoxyribonuclease.
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PMID:Isolation of Bacillus subtilis genes from a charon 4A library. 626 Jul 47

Here we report the cloning and preliminary characterization of the Pst I restriction-modification system of Providencia stuartii 164. Transformants of Escherichia coli carrying the Pst I gene system inserted into the cloning vector pBR322 were selected on the basis of acquired resistance to bacteriophage lambda infection. Pst I endonuclease was detected in osmotic shock fluid from each of the resistant clones. Plasmid and chromosomal DNA from these clones could not be digested by Pst I, indicating that the gene for the corresponding modification enzyme had also been cloned and was being expressed. The smallest recombinant plasmid encoding both activities, pPst201, contains an insert of approximately 4000 base pairs. In vitro transcription studies indicate that this DNA fragment also contains the endogenous promoter(s) of the system. When pPst201 was introduced into a minicell-producing strain of E. coli, two new proteins, 32,000 and 35,000 daltons, were synthesized. We have assigned these to the Pst I modification (methylase) and restriction enzymes, respectively. The active form of the restriction enzyme is a dimer, as determined by gel filtration. Constructed transformants of P. stuartii 164 that carry the Pst I system inserted into pBR322 produce approximately 10 times more Pst I endonuclease activity than does the native strain.
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PMID:Cloning and expression of the Pst I restriction-modification system in Escherichia coli. 626 7

Mycoplasma virus L2 is subject to host-specific restriction and modification in Acholeplasma laidlawii strains JA1 and K2. We have examined the DNAs from both host cells and viruses propagated on these strains with respect to susceptibility to cleavage by restriction endonucleases and for DNA base modifications. We show that, in strain K2 and L2 virus grown on K2 cells, cytosine in the sequence GATC is methylated to 5-methylcytosine and, although strain K2 and L2 viruses grown on K2 contain N6-methyladenine in their DNA, adenine in the sequence GATC is not methylated. In contrast to K2, strain JA1 and L2 virus grown on JA1 cells contain no detectable methylated bases. It is not known which of the methylated bases in K2 is the basis for the K2 restriction-modification system operative on L2 virus.
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PMID:Cytosine methylation of the sequence GATC in a mycoplasma. 628

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

Further research on bacteriophage T7 DNA penetration mechanism into E. coli cells during the infection was carried out. The DNA-RNA-hybridization on nitrocellulose filters revealed that in the presence of chloramphenicol the T7 DNA penetration from the virion into a host cell was coupled with its transcription by the bacterial RNA polymerase. The data obtained indicate that in the absence of antibiotics the penetration of a part of T7 genome which correspondes to class II and III genes is coupled with its transcription by a phage-specific RNA polymerase. Along with this the host restriction-modification system when its activity is not inhibited by the phage-induced proteins will be able to cleave the penetrated T7 DNA just after its transcription was accomplished. Considering these data along with our conception on direct involvement of transcription in T7 DNA penetration process during the infection one can suggest that E. coli RNA polymerase molecules which provide the phage DNA transport, are localized at the inner surface of cytoplasmic membrane.
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PMID:[Coupling of bacteriophage T7 DNA penetration with its transcription, during infection]. 635 19

Five individual DNA-cytosine methylases differing in pI (isoelectric point) values are present in Shigella sonnei 47-cells. The sequence specificity of each of those was determined 'in vitro' by a highly efficient combined approach that included pyrimidine tract (isostic) analysis, identification of the immediate neighbourhood of the methylated base within the recognition sequence and the calculation method. The enzyme with pI 5.3 (MSso5.3) is the counterpart of the RSso 47 II in the Sso 47 II restriction-modification system and methylates the internal cytosine residue of the 'palindromic' 5'-C-C-N-G-G-3' sequence. The enzymes with pI 6.2 (MSso6.2) and 7.4 (MSso7.4) exhibit identical specificity upon methylation of the 'palindromic' 5'-Py-C-N-G-Pu-3' sequence, but differ in the pI values of the proteins. The enzyme with pI 4.2 (MSso4.2) recognizes the unique tetranucleotide 5'-C-C-C-C-3' sequence and methylates the second cytosine residue at the 5'-end of the sequence. The enzyme with pI 8.4 (MSso8.4) methylates the central cytosine residue within the degenerative trinucleotide 5'-(PuC)-C-C-3' sequence. MSso5.3, MSso6.2, and MSso7.4 are presumed to belong to the 'family' of sequence-specific (Eco RII-like) enzymes. These DNA-cytosine methylases are likely to be evolutionary related to Eco RII and to have undergone a sufficient genetic drift so as to recognize similar (but more degenerative) nucleotide sequences.
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PMID:Sequence specificity of isolated DNA-cytosine methylases from Shigella sonnei 47 cells. 639 68

During transformation of B. subtilis cells with the Bsu R restriction-modification system by means of pUB110 plasmid restriction and modification of the plasmid DNA occurs. The effect of restriction on the transformation frequency is relatively weak, bringing about 20-fold decrease only. When using cells of a modifying recipient, the frequency of AR9 phage-mediated transduction of unmodified plasmid DNA is also relatively little decreased. The frequency of transduction by chromosomal markers, under the same conditions, falls much lower.
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PMID:Transformation and transduction of Bacillus subtilis strains with the Bsu R restriction-modification system by means of modified and unmodified DNA of pUB110 plasmid. 677 30

The presence of DNA host specific system in Shigella sonnei 47843 bacteria has been demonstrated. Phage DDIII grown on the cells of Shigella stutzeri 2, in Shigella sonnei 47843 cells is restricted by a factor of 105. Phage T3 of Eco B phenotype as well as DDIII phage is restricted in these cells. This circumstance means that the restriction-modification system of Shigella sonnei 47843 differs in specificity from the well known system E. coli. The results obtained are the second case of host specific system identification in Shigella. The biological properties of the strain (form of the colonies, colicinogenic activity, antibiotic resistance, ability to ferment sugars, etc.) have been studied.
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PMID:[Detection of the host specificity system in shigellae]. 700 Feb


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