In vivo functional interaction between DNA polymerase and dCMP-hydroxymethylase of bacteriophage T4

Some mutations in the structural gene for T4 DNA polymerase (gene 43) behave as suppressors of a deficiency in T4 dCMP-hydroxymethylase (gene 42). The suppression appears to involve a functional interaction between the two enzymes at the level of DNA replication. The hydroxymethylase deficiency caused DNA structural abnormalities in replication, and DNA polymerase lesions appeared to partially reverse these abnormalities. The results do not necessarily imply protein-protein interactions between the two enzymes, although both enzymes appear to play roles in controlling the fidelity of phage DNA replication.

The effects of aldosterone and spironolactone on renal kallikrein in the rat

1. A technique has been developed for the measurement of kallikrein 'production' in rat renal cortical cells in suspension. 2. After preparative steps, column chromatography on DEAE-cellulose yielded a peak of alpha-N-tosyl-L-arginine methyl ester (Tos-Arg-OMe) esterase activity identical with kallikrein isolated from rat urine in respect of pH optimum, effects of inhibitors, biological activity and immunological properties. 3. The nutrient medium surrounding incubated cells contained measurable kallikrein activity, which was increased by aldosterone and decreased by spironolactone. 4. The results raised the possibility that kallikrein could be an aldosterone-induced protein.

Two-hour embedding procedure for intracellular detection of viruses by electron microscopy

An embedding method requiring only 2 h to complete and giving excellent ultrastructural preservation has been used for the rapid detection of viruses in tissue cultures. The method has also been applied successfully to mammalian tissue. It provides a rapid technique for identifying viruses isolated in tissue cultures, for screening cultures for adventitious agents, and for examining tissue biopsies for viruses.

Regulation of maltodextrin phosphorylase synthesis in Escherichia coli by cyclic adenosine 3', 5'-monophosphate and glucose

Cyclic adenosine 3', 5'-monophosphate (AMP) stimulates maltodextrin phosphorylase synthesis in Escherichia coli cells induced with maltose. A maximal effect occurs at 2 to 3 mM cyclic AMP. The action of cyclic AMP is specific, inasmuch as adenosine triphosphate, 3'-AMP, 5'-AMP, adenosine, and dibutyryl cyclic AMP are inactive. Glucose, alpha-methyl glucoside, 2-deoxyglucose, and pyridoxal 5'-phosphate repress maltodextrin phosphorylase synthesis. This repression is reversed by cyclic AMP. The action of cyclic AMP appears to be at the transcriptional level, since cyclic AMP fails to stimulate phosphorylase production in induced cells in which messenger ribonucleic acid synthesis has been arrested by rifampin or by inducer removal. The two other enzymes involved in the metabolism of maltose, amylomaltase and maltose permease, are also induced in this strain of E. coli and affected by glucose and cyclic AMP in a manner similar to phosphorylase.

Ribonucleotides covalently linked to deoxyribonucleic acid in T4 bacteriophage

Bacteriophage T4 was grown in the presence of labeled uridine. The deoxyribonucleic acid (DNA) of the phage was shown to contain covalently attached ribonucleotides. The label appears not to be internal in the DNA strands. Presumably, it is at the ends of the DNA strands and this may be related to DNA initiation.