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J M Buchanan

Publications and source records attributed to J M Buchanan.

At least 73 records · Page 4Linked to original sources
PubMed1972

Induction of a reductive pathway for deoxyribonucleotide synthesis during early embryogenesis of the sea urchin.

Cell-free extracts of Arbacia eggs (Arbacia punctulata) apparently do not contain an enzymatic system for the reduction of ribonucleotides to deoxyribonucleotides. However, during an interval of 5 hr after fertilization at 23 degrees , an enzymatic system is produced that is capable of catalyzing the reduction of CDP to dCDP in the presence of Mg(2+), ethylenediaminetetraacetate, ATP, and a reducing agent, dithiothreitol. The activity is first seen about 1 hr after fertilization, and reaches a peak at about 5 hr. The appearance of the ribonucleotide reductase is prevented by the addition of emetine or puromycin, inhibitors of protein synthesis, to the cells before fertilization. Inclusion of actinomycin D in the cell suspension at a concentration sufficient to inhibit synthesis of messenger RNA does not appreciably affect the production of the enzyme activity. Preexisting, maternal RNA is thus used for synthesis of reductase. Ribonucleotide reductase may, therefore, represent the first example of an enzyme system absent in unfertilized eggs that is produced in response to fertilization.

Adenosine Triphosphate↗
PubMed1972

DNA-directed synthesis in vitro of T4 phage-specific enzymes.

The synthesis of deoxynucleotide kinase (EC 2.7.4.2) in vitro by a preparation consisting of T4 bacteriophage DNA and a cell-free extract of Escherichia coli has been reported. A study of the role of monovalent cations in the synthesis of this enzyme as well as alpha-glucosyl transferase (EC 2.4.1.2) shows that potassium ions are required for maximal enzyme production. Examination of the RNA-directed system indicates that potassium ions are more effective than ammonium ion in the translation of messenger RNA for the formation of the biologically active proteins studied. From a comparison of the magnitude of the effect of ions on both the DNA- and RNA-directed systems, we conclude that potassium ions may also have a marked stimulatory effect on transcription of the deoxynucleotide kinase gene of T4 DNA. The time required for messenger initiation and completion and the size distribution of messenger RNA formed in vitro were also examined.

Carbon Isotopes↗
PubMed1971

Vasectomy.

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Humans↗
PubMed1971

In vitro synthesis of deoxynucleotide kinase programmed by bacteriophage "T4-RNA.

RNA extracted from T4 phage-infected Escherichia coli cells can direct the synthesis of phage-specific deoxynucleotide kinase in a cell-free system from uninfected E. coli. The maximum messenger activity is obtained 8 min after infection at 37 degrees C and decreases there-after. The main activity of this messenger RNA has a sedimentation coefficient of about 15 S on a sucrose density gradient. The conditions necessary for the appearance of enzyme activity in vitro are the same as those required for de novo synthesis of protein. RNA from cells infected with a T4 amber mutant incapable of inducing the kinase in vivo lacks the ability to direct the synthesis of enzyme in vitro.

Carbon Isotopes↗