Herein, we describe β-selective coupling between a modified uracil and a deoxyribose to produce functionalized nucleosides catalyzed by thymidine phosphorylase derived from Escherichia coli. This enzyme mediates nucleobase-exchange reactions to convert unnatural nucleosides possessing a large functional group such as a fluorescent molecule, coumarin or pyrene, linked via an alkyl chain at the C...

Archaeal family-B DNA polymerases bind tightly to deaminated bases and stall replication on encountering uracil in template strands, four bases ahead of the primer-template junction. Should the polymerase progress further towards the uracil, for example, to position uracil only two bases in front of the junction, 3'-5' proof-reading exonuclease activity becomes stimulated, trimming the primer a...

The synthesis of the pyrimidinyl amino acids willardiine and isowillardiine was studied in vivo and in vitro. Uracil derivatives stimulate the biosynthesis of both compounds; the free base is the most effective. Significant incorporation of [2-(14)C]uracil and [6-(14)C]orotate into willardiine and isowillardiine was found. Incorporation of [6-(14)C]orotate was substantially decreased in the pre...

A uracil phosphoribosyltransferase (UMP-pyrophosphorylase) was found in several angiosperms and was partially purified from epicotyls of pea (Pisum sativum L. cv. Alaska) seedlings. Its pH optimum was about 8.5; its required approximately 0.3 mm MgCl(2) for maximum activity but was inhibited by MnCl(2); its molecular weight determined by chromatography on Sephadex G-150 columns was approximatel...

The wobble hypothesis does not discriminate between uracil and thymine. Methylation could favor further stabilization of uracil in the keto form. Thymine is present in keto form only and can pair up but with adenine. Uracil can easily construct the enol form; that is why it forms the U-G pair. In previous E-print I proposed an alternative to the wobble hypothesis [1]. According to my reviewers ...

The coinparntivc potencies of uracil mid thiouracil in terms of thyroidal changes, hypercholcstcrcinin, azoteniia, and incipient atherosclerosis were determined in rats fed cholesterol and cholic acid. Higher dietary levels of uracil were required to produce changes similar to those seen with thiouracil. Certain dietary components related to uracil were also studied. Orotic acid was found to ha...

BDF1 mice bearing L1210 leukemia, when treated with a regimen of uracil and methotrexate, show an increase in survival time greater than when treated with methotrexate alone. The uracil and methotrexate regimen also delays the development of methotrexate resistance as L1210 leukemia is transferred with therapy through multiple generations of mice. When uracil is applied to multiple generations ...

During spectrophotometric titrations of uracil in different alkalior alkali earth chlorides, specific changes in the U.V. absorption of uracil at PH 12.0 have been observed. The spectra of 4-methyl and 5-methyl uracil change in the same way whereas 1-methyl and 3-methyl uracil are not influenced even by strong divalent cations. From spectrophotometric and Potentiometrie titrations I I it could ...

Base moieties in DNA are spontaneously threatened by naturally occurring chemical reactions such as deamination, hydrolysis and oxidation. These DNA modifications have been considered to be major causes of cell death, mutations and cancer induction in organisms. Organisms have developed the DNA base excision repair pathway as a defense mechanism to protect them from these threats. DNA glycosyla...

BACKGROUND Saccharomyces boulardii (S. boulardii) is the best known probiotic yeast. The genetic engineering of this probiotic strain requires the availability of appropriate mutants to accept various gene constructs carrying different selection markers. As the auxotrophy selection markers are under focus, we have generated a ura3 auxotroph mutant of S. boulardii for use in further genetic mani...