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Query: EC:2.1.1.113 (restriction-modification system)
 350 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The genes for a Class II restriction-modification system (HhaII) from Haemophilus haemolyticus have been cloned in Escherichia coli. The vector used for cloning was plasmid pBR322 which confers resistance to tetracycline and ampicillin and contains a single endonuclease R-PstI site, (formula: see text), in the ampicillin gene. The procedure developed by Bolivar et al. (1977) was used to form DNA recombinants. H. haemolyticus DNA was cleaved with PstI endonuclease and poly(dC) extensions were added to the 3'-OH termini using terminal deoxynucleotidyl transferase. Circular pBR322 DNA was cleaved to linear molecules with PstI endonuclease and poly(dG) extensions were added to the 3'-OH termini, thus regenerating the PstI cleavage site sequences. Recombinant molecules, formed by annealing the two DNAs, were used to transfect a restriction and modification-deficient strain of E. coli (HB101 r-m-recA). Tetracycline-resistant clones were tested for acquisition of restriction phenotype (as measured by growth on plates seeded with phage lambdacI-0). A single phage-resistant clone was found. The recombinant plasmid, pD110, isolated from this clone, had acquired 3 kilobases of additional DNA which could be excised with PstI endonuclease. In addition to the restriction function, cells carrying the plasmid expressed the HhaII modification function. Both activities have been partially purified by single-stranded DNA-agarose chromatography. The cloned HhaII restriction activity yields cleavage patterns identical to HinfI. A restriction map of the cloned DNA segment is presented.
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PMID:Cloning of restriction and modification genes in E. coli: the HbaII system from Haemophilus haemolyticus. 35 Jul 14

The Escherichia coli-Brevibacterium lactofermentum shuttle vector pBLA was introduced into intact cells of B. lactofermentum by electrotransformation. Several parameters of this procedure such as voltage and cell concentration were analysed. Optimal conditions gave an efficiency of 10(6) transformants per microgram of DNA. Two recalcitrant strains could be electrotransformed when an ampicillin pretreatment step was used. Electrotransformation experiments using DNAase or different structural forms of plasmid DNA showed that the electrotransformation process is quite different from natural transformation involving competence development. Restriction-modification-proficient B. lactofermentum could be efficiently electrotransformed with pBLA DNA isolated from E. coli. This restriction-modification system therefore seems to be overcome by electrotransformation. Thus electrotransformation may efficiently replace the protoplast bacterial transformation method.
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PMID:Transfer of plasmid DNA to Brevibacterium lactofermentum by electrotransformation. 226 76

No transformant was obtained when pCZA168(bla, tsr, Tn5096, ColEI rep. Strep repts) was used to transform S. hygropinocus RF220. pIJ702 isolated from S. hygroscopicus N103 was transformed into RF220 at a low frequency. pIJ702 plasmid was cured in RF220 transformant and it was re-transformed into its cured FR220 strain, but the transformation frequency was not increased significantly, suggesting that restriction-modification system in FR220 was existent and complicated. Four transformants containing pCZA168 were obtained, when the RF220 strain was grown in medium with ampicillin, glycine and the protoplast was stored at -70 degrees C. Restriction analysis of plasmid from transformants indicated that the DNA fragment from E. coli in pCZA168 was deleted. With transposition of Tn5096, two mutants blocked in antibiotic biosynthesis of 120 and some mutants with variation in antibiotic level were obtained, this showed that the Tn5096 transposed in different positions of chromosomal DNA in RF220 and resulted in the production of 120 in different level.
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PMID:[Transposition of Tn5096 in a agricultural antibiotic 120 roducer Streptomyces hygrospinocus var. beijingensis RF220]. 1255 55