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J Josephsen

Publications and source records attributed to J Josephsen.

8 recordsLinked to original sources
PubMed1995

Restriction-modification systems in Lactococcus lactis.

Several restriction-modification (R-M) systems have been identified in Lactococcus lactis. Most of the systems have been plasmid encoded and function as phage-resistance mechanisms. At least five different type-II R-M systems, LlaAI, LlaBI, LlaCI, LlaDI and LlaEI, were identified in isolates from a mixed Cheddar starter culture. LlaAI and LlaBI recognized the DNA sequences 5'- decreases GATC-3' and 5'-C decreases TRYAG-3', respectively. The genes coding for the LlaAI and LlaBI R-M systems have been cloned and sequenced. The LlaAI R-M system had two genes coding for methyltransferases (MTases) and one gene coding for a restriction endonuclease (ENase). The MTases showed high homology to the MTases from DpnII. The LlaBI R-M system had one gene coding for a MTase and one gene coding for an ENase.

Base Sequence↗
PubMed1990

Stacking of three different restriction and modification systems in Lactococcus lactis by cotransformation.

Four plasmids encoding restriction and modification (R/M) systems are described that are different in the specificity of their restrictive activity toward the small isometric phage p2 and prolate phage c2. The R/M plasmids were cotransformed into Lactococcus lactis MG1363 with pVS2, encoding resistance to chloramphenicol and erythromycin, to indicate successful transformation events. Analysis of cotransformants showed that three different R/M plasmids could be combined in L. lactis MG1363. The efficiency at which phage plaqued on the transformants decreased as the number of R/M plasmids increased. Some plasmid combinations were unstable suggesting replicon incompatibility.

Chloramphenicol Resistance↗
PubMed1989

CRP/cAMP- and CytR-regulated promoters in Escherichia coli K12: the cdd promoter.

Transcriptional regulation of the deoP2 promoter by the cyclic AMP/cyclic AMP receptor protein complex (cAMP/CRP) and the CytR repressor requires two high-affinity CRP targets located around -41 and -93 bp preceding the start site for transcription. Here we report the structure of cddP, another CRP/CytR-regulated promoter. In common with what was found in deo, the cdd promoter also contains multiple CRP targets. Thus, using the DNasel footprinting procedure, tandem CRP binding sites were identified around -41 and -93. These findings support a general model for CytR binding and CytR regulation, in which (i) CytR and the CRP/cAMP complex bind to similar or identical targets, (ii) two or more targets are necessary for proper binding of CytR to a promoter region, and (iii) CytR represses transcription by antagonizing cAMP/CRP activation.

Base Sequence↗
PubMed1985

Phosphate buffer and salt medium concentrations affect the inactivation of T4 phage by platinum(II) complexes.

The initial rate of inactivation of T4 phage by solutions of [Pt(NH3)2Cl2], [PtenCl2] and [Pten(H2O)2] (NO3)2 at fixed values of pH is strongly reduced by phosphate buffer, slightly reduced by acetate buffer and apparently not influenced by bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane (BIS-Tris) buffer and HEPES buffer. The phosphate abolishes the antiphage activity of the platinum complexes probably by some sort of complex formation. This together with dimerization reactions qualitatively explains the tailing off of the phage inactivation rate. High concentrations of NaNO3 as the salt medium give increased phage inactivation rates, which are also strongly pH-dependent.

Buffers↗
PubMed1982

Complement mediated lysis in chickens.

Rat erythrocytes, when either injected i.v. into chickens, or incubated in vitro with chicken serum, will be lysed within minutes. This lysis is complement dependent but does not involve specific antibodies since Ig-free bursectomized chickens behave in exactly the same way as normal chickens with high levels of haemagglutinating antibodies. The lysis is mediated by activation of complement component C3 via the alternative complement pathway and various observations lead us to doubt the functional existence in this lytic reaction of the classical complement pathway.

Animals↗
PubMed1981

Fusion of the lac genes to the promotor for the cytidine deaminase gene of Escherichia coli K-12.

Phage Mu has been inserted into the structural gene for cytidine deaminase (cdd). By the use of phage lambda (lac, Mu) the promoter for the cdd gene has been fused to lacZ. In these strains lacZ expression is regulated by the cytR repressor protein and is therefore induced by cytidine. The fusion strains were used for the isolation of cddo mutants. Plaque forming lambda phages carrying the different cdd-lacZ fusions were isolated. Studies of the cdd-Mu strains showed that the cdd gene is transcribed clockwise with respect to the Escherichia coli map.

Bacteriophage lambda↗
PubMed1979

Platinum(II) complexes block the entry of T4 phage DNA into the host cells.

The efficiency of multiplicity reactivation of T4 particles inactivated by platinum(II) complexes is very low. The same is true for marker rescue and functional survival of genes. This can be at least partly explained by the inability of most inactivated virus particles to introduce their DNA into the host cells as demonstrated by electron microscopy. Conformational changes in the DNA, formation of DNA-DNA and DNA-protein cross-links and the damage of proteins participating in the injection process could be responsible for the phenomenon observed.

Cisplatin↗