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Biomedical subjects

N D Zinder

Publications and source records attributed to N D Zinder.

At least 73 records · Page 4Linked to original sources
PubMed1975

Site-specific cleavage of single-stranded DNA by a Hemophilus restriction endonuclease.

Single-stranded viral DNA of bacteriophage f1 is cleaved into specific fragments by endo R-HaeIII, a restriction endonuclease isolated from Hemophilus aegyptius. The sites of the single strand cleavage correspond to those of the double strand cleavage. A single-stranded DNA fragment containing only one HaeIII site is also cleaved by this enzyme. This observation suggests that the reaction of single-stranded DNA cleavage does not require the formation of a symmetrical double-stranded structure that would result from the intramolecular base-pairing between two different HaeIII sites. Other restriction endonucleases may also cleave single-stranded DNA.

Base Sequence↗
PubMed1975

Endonuclease R-EcoRII restriction of bacteriophage f1 DNA in vitro: ordering of genes V and VII, location of an RNA promotor for gene VIII.

Replicative form DNA of bacteriophage f1 was found to be sensitive in vitro to restriction by endonuclease R-EcoRII if the DNA was isolated from an Escherichia coli strain deficient in cytosine methylase activity. A similar observation was previously made with DNA from the closely related bacteriophage fd (S. Schlagman, S. Hattman, M. S. May, and L. Berger, submitted for publication). The two DNA fragments produced by the endo R-EcoRII digestion of f1 DNA were localized on the f1 cleavage map and their genetic content was determined. The polypeptides synthesized in a "coupled" transcription-translation system under the direction of each RII fragment were examined. The results of such experiments allow the ordering of genes V and VII and indicate the location of a RNA promotor for gene VIII.

Chromosome Mapping↗
PubMed1974

Kinetics of methylation of DNA by a restriction endonuclease from Escherichia coli B.

The restriction endonuclease from E. coli B is both an endonuclease and a DNA methylase. Both activities either require or are stimulated by Mg(+2), adenosine triphosphate, and S-adenosyl-L-methionine. The particular activity which the enzyme exhibits depends upon the nature of the SB sites, the genetic sites that identify substrate DNA. Enzymatic treatment of DNA that has an unmodified, wild-type SB site results in either rapid restriction of the DNA or very slow methylation of the SB site. On the other hand, a hybrid SB site (modified), which protects the DNA molecule from restriction, results in rapid methylation of that SB site.

Adenosine Triphosphate↗
PubMed1974

Highly purified colicin E3 contains immunity protein.

Colicin E3, even when highly purified, still contains about one molar equivalent of a second protein, "E3 immunity protein." The two proteins are bound together in a complex that can be dissociated only under strongly denaturing conditions, such as electrophoresis in sodium dodecyl sulfate-polyacrylamide gles or by gel filtration in 6 M guanidine.hydrochloride. Colicin and immunity protein were separated by preparative electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. The immunity protein prepared in this way was shown to be functionally and immunologically identical to immunity protein purified from colicinogenic cells by other methods. Colicin E3 that had been freed of immunity protein was much more active than complexed colicin in inhibiting protein synthesis in vitro.

Animals↗
PubMed1973

Resistance to colicins E3 and K induced by infection with bacteriophage f1.

When infected with the filamentous phage f1, Escherichia coli K-12 strains are 20- to 40-times more resistant to colicins K and E3 than are uninfected cells. The colicins are adsorbed normally and are blocked in their action at some subsequent stage of their action. Productive infection of virions is not necessary for induction of resistance. The evidence presented implicates the product of gene III of the phage, a minor protein in the virion, as being responsible for this resistance. The simplest interpretation of the results is that this gene product blocks the penetration of colicins which is necessary for their action.

Adsorption↗
PubMed1972

Cleavage of bacteriophage fl DNA by the restriction enzyme of Escherichia coli B.

We studied the cleavage of the replicative-form DNA (RF I) of bacteriophage f1 and its SB mutants by purified restriction endonuclease of E. coli B. The results indicate that: (i) Circular replicative forms are broken once to yield full-length linear molecules (RF III). Such linear molecules are less susceptible than RF I to endonuclease R-B. (ii) The genetic sites (SB sites) that confer on the DNA susceptibility to B-restriction are not the actual sites of cleavage. The number of possible cleavage sites is larger than the number of SB sites. We conclude this because an RF III molecule produced by endonuclease R-B from RF I of a mutant that has only one SB site can be circularized by denaturation and renaturation. (iii) The SB site is not modified when the DNA is cleaved, since an SB site can be used repeatedly by endonuclease R-B; the RF III described in ii can be cleaved by the same enzyme after denaturation and renaturation.

Carbon Isotopes↗