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

A method for mutagenizing circular DNA molecules has been developed that uses synthetic oligodeoxynucleotide restriction sites as mutagens. A single synthetic restriction site is introduced at random by cleaving circular DNA with a nonspecific double-strand endonuclease. The restriction site is then ligated to the ends and the molecule is subsequently recircularized. These small additions to the genome are mapped by digestion with the appropriate restriction enzyme. Rearrangements such as duplications and deletions can be engineered at will by using the added restriction sites. This technique has been used to produce a fine-structure map of RSF1050, a ColE1 derivative, 60% of which is a transposable DNA sequence encoding the TEM beta-lactamase (Tn3). A subset of the mutations, mapping within a narrow region of Tn3, result in an increased frequency of Tn3 transposition; mutations in other regions abolish transposition entirely.
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PMID:In vitro mutagenesis of a circular DNA molecule by using synthetic restriction sites. 36 7

By restriction endonuclease cleavage mapping and electron microscopic examination of heteroduplexes, we have identified an ampicillin resistance determinant transposon, designated Tn1701, in a group of small, nontransferring plasmids which confer resistance to ampicillin (Ap), sulfonamide (Su), and streptomycin (Sm). Plasmid NTP1, which mediates Ap resistance, contains Tn1701. Recombinant plasmids NTP3 (Ap Su) and NTP4 (Ap Su Sm) contain Tn1701, indicating that they were derived by transposition of Tn1701 from NTP1 to an unrelated plasmid, NTP2 (Su Sm). The transposon Tn1701 is very similar to the known ampicillin resistance transposons Tn1, Tn2, and Tn3 in its size (3.2 x 10(6) daltons), base sequence homology observed by heteroduplex formation, restriction endonuclease cleavage sites, and possession of a short inverted repeat sequence at both ends. Like the other TnA elements, Tn1701 also specifies a type TEM beta-lactamase.
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PMID:Location of an ampicillin resistance transposon, Tn1701, in a group of small, nontransferring plasmids. 37 Jan 8

The genetic environment of plasmid-borne blaTEM mutant genes, encoding nine distinct TEM-type extended-spectrum beta-lactamases, was studied in transconjugants from clinical isolates of enterobacteria. Colony hybridization with probes specific for tnpA and tnpR of Tn3, tnpA and tnpI of Tn21, aacA4, and IS15, and restriction endonuclease analysis of plasmid DNA indicated that the structural genes for the enzymes were always associated with intact or deleted variants of the Tn3 family. Four of the nine blaTEM variants, which account for 62% of 222 isolates in a molecular epidemiological study, were associated with replicons indistinguishable from the epidemic Inc7-M plasmid pCFF04 that carries the blaTEM-3 gene. This suggests that mutant genes were selected from the same prototype plasmid carrying penicillinase genes blaTEM-1 or -2. A 6.6 kb DNA fragment of pCFF04 containing blaTEM-3 was characterized by amplification mapping and sequencing. The results obtained indicated that blaTEM-3 was present on a copy of Tn1 interrupted at the start codon of the transposase by a DNA sequence reminiscent of the inverted repeats of class II transposons. This partial Tn1 copy was in turn, inserted into the transposase gene of a Tn21-like transposon containing an integron expressing an aacA4 gene. The presence of an integron can account for the various assortments of aminoglycoside resistance genes found associated with blaTEM-3.
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PMID:A new example of physical linkage between Tn1 and Tn21: the antibiotic multiple-resistance region of plasmid pCFF04 encoding extended-spectrum beta-lactamase TEM-3. 133 47

High level tetracycline resistant strains of Neisseria gonorrhoeae (TRNG) have been shown to carry a 40.6 kb (25.2 MDa) conjugative plasmid with a Class M tetracycline resistance determinant. Restriction endonuclease analysis mapping showed that there were at least two different TRNG plasmid types which were found in geographically distinct locations. The physical maps of these two plasmids were compared to a gonococcal conjugative plasmid which did not encode tetracycline resistance. The plasmid type which is endemic in the Netherlands was found to be closely related to the gonococcal conjugative plasmid, which supports the established hypothesis that the 40.6 kb plasmid has evolved by transposition of the TetM determinant into the conjugative plasmid. The plasmid found in the United States has either evolved by substantial divergent evolution or it results from a different transposition event. In the UK there have been isolations of TRNGs carrying either of the two plasmid types reflecting a flow of people both across the Atlantic and in Europe. It is possible that further TetM-containing plasmids will be found in N. gonorrhoeae paralleling the family of TEM beta-lactamase encoding plasmids already described.
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PMID:Molecular evolution of tetracycline-resistance plasmids carrying TetM found in Neisseria gonorrhoeae from different countries. 177 50

Eleven clinical isolates of Klebsiella oxytoca from Stockholm hospitals were found to be resistant to aztreonam and cefuroxime, but susceptible to cefotaxime, ceftazidime and imipenem. Resistance could be overcome by combining the beta-lactams with the inhibitor clavulanic acid. Crude beta-lactamase preparations from the isolates inactivated aztreonam and cefuroxime rapidly. By isoelectric focusing, a single common beta-lactamase of pI 5.25 was detected. The K. oxytoca isolates belonged to three subgroups, based on their plasmid profiles and Bg/II restriction endonuclease digestion of plasmid DNA. It was concluded that resistance to aztreonam and cefuroxime in these isolates was conferred by a beta-lactamase distinct from TEM-1, TEM-2 and SHV-1, but possibly derived from TEM-like enzymes.
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PMID:Characterization of Klebsiella oxytoca septicaemia isolates resistant to aztreonam and cefuroxime. 196 Jan 20

A total of 33 clinical isolates encoding TEM-3 (CTX-1) from four French hospitals were studied. The strains belonged to seven species, Klebsiella pneumoniae (n = 24), Escherichia coli (n = 3), Serratia marcescens (n = 2), Citrobacter freundii (n = 1), Enterobacter aerogenes (n = 1), Enterobacter cloacae (n = 1), and Klebsiella oxytoca (n = 1). All the strains harbored an Inc7 or M self-transferable plasmid with a size of approximately 85 kilobases. The plasmids had closely related EcoRI, HincII, HindIII, and PvuII restriction endonuclease-generated patterns and conferred resistance to all beta-lactams, except cephamycins and imipenem; to tetracycline, because of the presence of the genes blatem-3 and tetC, respectively, as determined by hybridization with specific probes; and to sulfonamide. Depending on the presence or absence and level of expression of the genes aacA4, aadA, and dfrI and of insertion element IS15, four types of plasmids could be distinguished. Plasmid pCFF04, the prototype plasmid encoding TEM-3, was widespread and appeared, by Southern hybridization, as the progenitor of the other types of replicons. The plasmid epidemic responsible for dissemination of TEM-3 in clinical isolates of members of the family Enterobacteriaceae may have originated in S. marcescens since pCFF04 was first detected in this species.
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PMID:Molecular epidemiology of TEM-3 (CTX-1) beta-lactamase. 232 69

Epidemiologic studies of plasmid-mediated resistance at the Cleveland Veterans Administration Medical Center revealed that related plasmids had disseminated among members of the family Enterobacteriaceae. We studied the beta-lactamases encoded by these plasmids in Escherichia coli C600 transformants or transconjugants. Substrate and inhibition profiles of the enzymes determined by two of these plasmids suggested an activity resembling TEM-1; however, isoelectric focusing revealed a pI of 7.0. These two plasmids were originally found in a Serratia marcescens (pDS076) and an Enterobacter cloacae (pDS075) strain isolated from the same sink in the medical intensive care unit and later, in an Enterobacter cloacae (pDS142 identical to pDS076) isolate colonizing a patient in the same unit. The plasmids also carried the aminoglycoside resistance determinant, 2"-aminoglycoside nucleotidyl transferase. A 2-kilobase AvaI restriction endonuclease digestion fragment of pSD075 known to carry the beta-lactamase determinant was used as a molecular probe. This probe did not recognize sequences of any plasmid-mediated beta-lactamase tested including the recently described determinants ROB-1, TLE-1, and OXA-4-7. A TEM-1 probe derived from the 0.7-kilobase PstI-EcoRI fragment of pBR322 failed to recognize the new beta-lactamase gene. Four additional Enterobacter cloacae and two Enterobacter aerogenes strains isolated in Columbus, Ohio, have been shown to produce a pI 7.0 beta-lactamase and to carry plasmids recognized by the 2-kilobase probe. These data suggest dissemination of a novel plasmid-mediated beta-lactamase among members of the family Enterobacteriaceae in Ohio and demonstrate the development and utility of a molecular probe for the new determinant. We suggest that the novel beta-lactamase be named OHIO-1.
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PMID:Novel plasmid-mediated beta-lactamase in members of the family Enterobacteriaceae from Ohio. 349 Feb 15

Three Haemophilus parainfluenzae strains isolated from the urogenital tract harbored a beta-lactamase-coding 3.2-megadalton plasmid identical, by restriction endonuclease digestion and hybridization with radioactive and biotin-labeled probes specific for the TEM-1 beta-lactamase and TnA sequences, to the 3.2-megadalton "African-type" plasmid found in Neisseria gonorrhoeae.
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PMID:Isolation and molecular characterization of beta-lactamase-producing Haemophilus parainfluenzae from the genital tract. 349 10

A prevalence study was carried out on a 100-bed Veterans Administration nursing home care unit to determine the extent of colonization with gentamicin-resistant gram-negative bacilli (GRGNB). Hand cultures of 12 employees and 17 environmental cultures were negative. Twenty-six of 86 (30%) patients were colonized with 49 GRGNB. Sixteen patients (19%) had urinary colonization. Multivariate analysis revealed significant associations between rectal or perineal colonization (P less than 0.01), and the presence of a urinary device (82% condom catheters) (P less than 0.05), with urinary colonization. The most common isolates were Providencia stuartii (20), Escherichia coli (nine) and Klebsiella pneumoniae (nine). Twenty-six of 49 isolates carried plasmids. Restriction endonuclease digestion of plasmid DNA was performed for 21. Cross-colonization, as defined by the presence of the identical species with the identical restriction endonuclease digestion profile of purified plasmid DNA found in different patients, was observed for eight of 21 (38%) strains. All were geographically clustered. No strains could transfer gentamicin-resistance by conjugation and only two plasmids could transform our E coli recipient to gentamicin resistance. One E coli plasmid was identical to two Citrobacter freundii plasmids and a P stuartii plasmid isolated from three different patients. This 105 kb plasmid is conjugative and encodes resistance to ampicillin, carbenicillin, tetracycline, and sulfonamides. Thus, 57% of strains were cross-colonizing or contained identical R-plasmids. Southern hybridization using a 1 kb TEM-1 gene probe demonstrated sequences homologous to this probe in five of five nursing home plasmids examined.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Prevalence of colonization with antibiotic resistant gram-negative bacilli in a nursing home care unit: the importance of cross-colonization as documented by plasmid analysis. 353 83

The sizes of the zones of inhibition around routinely tested antibiotic disks classified gentamicin-resistant isolates of Klebsiella pneumoniae from one hospital into four major antibiotype classes. From each isolate of the prevalent class (A1), two plasmids could be transferred conjugally. One carried genes for resistance to tetracycline, sulfonamides, and chloramphenicol, and for the SHV beta lactamase. The other carried genes for two aminoglycoside-inactivating enzymes, APH (3')-I and AAC (3)-III, for the TEM 1 beta lactamase, and for resistance to sulfonamides. Transconjugants of either plasmid from any A1 isolate yielded the same DNA fragments after restriction endonuclease digestion, but the two plasmids had no fragments in common. Fragments or genes from either plasmid were variously combined or lacking in plasmids from variant isolates (A2, A3, and A4). Plasmids transferable from isolates of classes B and C shared no common DNA restriction fragments with each other or with either plasmid from Class A. Fragments and genes of the plasmids from C isolates, however, were identical with those of a plasmid endemic in a nearby hospital. Routine monitoring by diagnostic microbiology laboratories of distinctive antibiotypes and of the plasmids that produce them would aid infection control and antibiotic usage policy.
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PMID:Diagnostic microbiology laboratory susceptibility test results discriminate distinctive antibiotic resistance plasmids. 609 87


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