Escherichia coli phage N15 encodes the slightly acidic, 630-residue protein of 72.2 kDa called protelomerase (TelN). TelN is a component of the N15 replication system proposed to be involved in the generation of the linear prophage DNA. This linear DNA molecule has covalently closed ends. The reaction converting circular plasmids into linear molecules was catalyzed in vitro. We demonstrate that...

The prophage of coliphage N15 is not integrated into the bacterial chromosome but exists as a linear plasmid molecule with covalently closed ends. Upon infection of an Escherichia coli cell, the phage DNA circularises via cohesive ends. A phage-encoded enzyme, protelomerase, then cuts at another site, telRL, and forms hairpin ends (telomeres). We demonstrate that this enzyme acts in vivo on spe...

It is presumed that uric acid is an end-product of human metabolism and, as such, is not further catabolized. This presumption is based largely upon indirect evidence such as the failure to demonstrate uricase in human tissues and the uncertain r81e of allantoin in human metabolism. On the other hand, Folin presented evidence that uric acid intravenously injected into humans could not be quanti...

In recent years erotic acid (uracil-4-carboxylic acid) has been found to be essential for the growth of some microorganisms;l some pyrimidine-requiring Neurospora mutants were found to grow equally well with uracil and erotic acid2 and some mutants have been found to produce erotic acid.3 It has been suggested that erotic acid is a by-product in the biosynthesis of pyrimidines in Neurospora.s I...

It has been clearly established (1, 2), through the use of N16-labeled material, that the utilization of free thymine for the synthesis of deoxyribonucleic acid (DNA) by the rat is extremely limited. However, these studies afforded but little information concerning the rate and extent of the metabolism of thymine. In the experiments reported here, thymine-204 has been found to be more rapidly a...

Temperate bacteriophages possess a genetic switch which regulates the lytic and lysogenic cycle. The genomes of the temperate telomere phages N15, PY54, and ϕKO2 harbor a primary immunity region (immB) comprising genes for the prophage repressor (cI or cB), the lytic repressor (cro) and a putative antiterminator (q). The roles of these products are thought to be similar to those of the lambda p...

Aminoacridines have a long history in the drug and dye industries and display a wide range of biological and physical properties. Despite the historical relevance of 9-aminoacridines, there have been few studies investigating their stability. 9-Aminoacridines are known to hydrolyze at the C9-N15 bond, yielding acridones. In this study, the pH-dependent hydrolysis rates of a series of 9-substitu...

Sequence-specific DNA-binding proteins must quickly and reliably localize specific target sites on DNA. This search process has been well characterized for monomeric proteins, but it remains poorly understood for systems that require assembly into dimers or oligomers at the target site. We present a single-molecule study of the target-search mechanism of protelomerase TelK, a recombinase-like p...

Available data on the isotopic ratio See PDF for Equation of ammonia (r(a)) and that of urea (r(u)) after a single feeding of glycine, aspartic acid, and ammonium citrate are analyzed. From this analysis the following conclusions are drawn. 1. The isotopic ratio See PDF for Equation of ammonia (r(a)) is always higher than that of urea (r(u)) in the initial period after a single feeding of isoto...

1. l-Aspartic acid labeled with N(15) was fed to one human adult and six infants, and the total N and N(15) were determined in the urine from time to time. 2. The N(15) concentration (or isotopic ratio) of urinary N reached its maximum in the adult about 2 hours and in the infants about 4 hours after feeding, then fell off logarithmically. 3. Assuming that the N of aspartic acid readily entered...