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

---

Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Eco57I restriction endonuclease and methylase were purified to homogeneity from the E.coli RR1 strain carrying the eco57IRM genes on a recombinant plasmid. The molecular weight of the denaturated methylase is 63 kDa. The restriction endonuclease exists in a monomeric form with an apparent molecular weight of 104-108 kDa. R.Eco57I also possesses methylase activity. The methylation activities of both enzymes modify the outer A residue in the target sequence 5'CTGAAG yielding N6-methyladenine. M.Eco57I modifies both strands of the substrate while R.Eco57I modifies only one. Only the methylase enzyme is stimulated by Ca2+. The restriction endonuclease shows an absolute requirement for Mg2+ and is stimulated by AdoMet. ATP has no influence on either activity of the enzymes. The subunit structure and enzymatic properties of the Eco57I enzymes distinguish them from all other restriction-modification enzymes that have been described previously. Therefore, RM.Eco57I may be regarded as a representative of a novel class of restriction-modification systems, and we propose to classify it as type IV.
...
PMID:Purification and properties of the Eco57I restriction endonuclease and methylase--prototypes of a new class (type IV). 133 60

Conditions were determined for the methylation of intact yeast chromosomes by EcoRI, HhaI, and MspI bacterial methylases using an endonuclease protection assay while the chromosomes were embedded in agarose plugs suitable for transverse-field electrophoresis. Parameters were also established for the methylation of human chromosomes by EcoRI methylase. Methylation of embedded chromosomes by EcoRI methylase required prewashes with EDTA. EcoRI, HhaI, and MspI methylases showed optimal activity when nonacetylated bovine serum albumin, high levels of S-adenosylmethionine, and high levels of methylase were used. The use of bacterial methylases for methylation of embedded chromosomes will allow investigators to normalize variations in cellular DNA methylation prior to restriction and create new and rare endonuclease recognition sites which will facilitate the detection of chromosomal alterations and deletions.
...
PMID:Methylation of intact chromosomes by bacterial methylases in agarose plugs suitable for pulsed-field electrophoresis. Methylation of intact chromosomes in agarose by methylases. 212 70

In Physarum flavicomum Berk., haploid myxamoebae convert to dormant microcysts under conditions of nutrient imbalance. Exogenous adenine increases the intracellular content of S-adenosylmethionine (SAM) and inhibits this process. However, treatments that reduce the intracellular SAM levels relieve the inhibition of encystment induced by adenine. SAM plays a major metabolic role in cellular transmethylation reactions. In this study, we compared the DNA methylation patterns of growing cells, encysting cells, adenine-inhibited cells, and cysts using three different approaches: incubation of the cells with [14C]methylmethionine and detection of the labeled methyl group in purified DNA samples; analyses of DNA base composition by high performance liquid chromatography; and restriction endonuclease analyses of DNA. We found that DNA from the adenine-treated cells was labelled 1.3 times more with [14C]methylmethionine than was the DNA of untreated encysting cells. The DNA G + C content of this species was about 41%. The DNA of growing cells had the highest 5-methylcytosine (5MC) content, while DNA from the cysts had the lowest (about 27% that of growing cells). Adenine-inhibited cells had about 1.2 times more DNA-5MC than did encysting cells. Using the restriction enzymes SmaI, PvuI, and XhoI (which are inhibited by C residue methylation), we found that cyst DNA had more cutting sites than did amoebal DNA. By using the restriction enzyme DpnI which cuts DNA at GmATC sites, we found that cyst DNA, but not growing cell DNA, contained N6-methyladenine.
...
PMID:DNA methylation pattern during the encystment of Physarum flavicomum. 216 19

A type II restriction endonuclease, named CviJI, was isolated from a eukaryotic Chlorella-like green alga infected with the dsDNA containing virus IL-3A. CviJI is the first restriction endonuclease to recognize the sequence PuGCPy; CviJI cleaves DNA between the G and C. Methylation of the cytosine in PuGCPy sequences prevents cleavage by CviJI. CviJI cleaved DNA into smaller but defined fragments in the presence of ATP. This "star" activity was stimulated by dithiothreitol and/or S-adenosylmethionine but did not occur under conditions which favor "star" activity of other restriction endonucleases.
...
PMID:IL-3A virus infection of a Chlorella-like green alga induces a DNA restriction endonuclease with novel sequence specificity. 281 20

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.
...
PMID:The EcoDXX1 restriction and modification system of Escherichia coli ET7. Purification, subunit structure and properties of the restriction endonuclease. 299 88

We have examined the DNA-protein interactions involved in the recognition of a specific hexameric sequence, GAATTC, by the EcoRI modification methylase by using derivatives of an oligodeoxyribonucleotide that contain a variety of base analogues. The base analogues 2-aminopurine, 5-bromocytosine, 5-bromouracil, 2,6-diaminopurine, hypoxanthine, 5-methylcytosine, N6-methyladenine, and uracil were incorporated as single substitutions into the octadeoxyribonucleotide d(pG-G-A-A-T-T-C-C). The effects of the substitutions on the ability of the enzyme to methylate the modified substrates were monitored by determining the steady state kinetic values of the reaction in the presence of the cosubstrate, S-adenosylmethionine. The substitutions resulted in effects ranging from complete inactivity to enhanced reactivity. The enzyme exhibited Michaelis-Menten kinetics with those analogues that were active, whereas the octanucleotides containing hypoxanthine at the guanine site, N6-methyladenine at the first or 2-aminopurine at the second adenine site, or uracil at the second thymine site were completely inactive. The results are discussed in terms of the possible interactions between the methylase and its recognition sequence. In addition, the interactions are compared to those of the EcoRI restriction endonuclease, which has been similarly tested with the same analogue oligonucleotides. The results of that study are reported in an accompanying paper. Although both enzymes recognize the same sequence, they do so in different ways.
...
PMID:The effects of base analogue substitutions on the methylation by the EcoRI modification methylase of octadeoxyribonucleotides containing modified EcoRI recognition sequences. 301 81

The gene expression of nine phages of the T7 group was compared after infection of Escherichia coli B(P1). With the exception of phage 13a which grew normally, all of them infected E. coli B(P1) abortively. Differences were found in the efficiency of host killing which ranged from 100% for phage 13a to 37% for phage A1122. Infection by T7 prevented colony formation by about 70% of the cells but they showed filamentous growth until about 2 h after infection. It was shown by SDS-polyacrylamide gel electrophoresis and autoradiography of [35S]methionine-labelled phage-coded proteins that all phages except for 13a showed measurable expression only of the early genes. No correlation was observed between killing capacity and the pattern of gene expression, and the ability to hydrolyse S-adenosyl-methionine (SAM, a cofactor for the P1 restriction endonuclease) by means of a phage-coded SAMase. Mixed infection of E. coli B(P1) with 13a and T7 yielded mixed progeny indistinguishable from that observed after mixed infection of the normal host E. coli B. Genetic crosses with amber mutants of 13a and T7 showed that the 13a marker opo+ (overcomes P one), required for growth on B(P1), is located in the early region, to the left of gene 1 (RNA polymerase gene).
...
PMID:Inhibition of gene expression of T7-related phages by prophage P1. 304 52

Previous comparison of the amino acid sequences of the GATC-methylating Escherichia coli Dam methyltransferase (MTase) with those of other adenine MTases (M.EcoRV, M.DpnII and T4Dam) localized four conserved regions. Regions III and IV have similarities with many other MTases. The sequence DPPY (or NPPY) is always present in region IV. It was suggested to be the AdoMet binding site. Publication of the nucleotide and amino acid sequences of M.CviBIII, M.DpnA and MutH give further credence to this assignment: M.DpnA, which also methylates GATC, has strong similarities with regions III and IV; M.CviBIII, a cytosine methylase, has a characteristic NPPY sequence in region IV, and only limited resemblance in region III; MutH, the GATC-specific endonuclease in DNA mismatch repair, has significant similarities uniquely in region III. The presently available evidence suggests that region III is the GAT(C) binding site and region IV is the AdoMet binding site. This hypothesis is strengthened by recent genetic findings.
...
PMID:The DNA and S-adenosylmethionine-binding regions of EcoDam and related methyltransferases. 307 10

The highly purified restriction endonucleases of E. coli K and coliphage P1 transfer methyl groups from S-adenosylmethionine to adenine residues of unmodified DNA. Incubation of unmodified DNA with endonucleases K or P and S-adenosylmethionine renders the DNA resistant to restriction. The enzymes, therefore, have both restriction endonuclease and modification methylase activities.
...
PMID:DNA modification methylase activity of Escherichia coli restriction endonucleases K and P. 456 4

In the presence of Mg(++), ATP, and S-adenosylmethionine, the DNA restriction endonuclease R.K forms a specific complex with its DNA substrate. The complex can be detected by its retention on nitrocellulose membranes.
...
PMID:A specific complex between a restriction endonuclease and its DNA substrate. 498 37


<< Previous 1 2 3 4 5 6 7 Next >>

---