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Biomedical subjects

I Tessman

Publications and source records attributed to I Tessman.

At least 55 records · Page 3Linked to original sources
PubMed1980

Suppression of polarity in the gal operon by ultraviolet irradiation.

The polarity of nonsense mutations in the galE gene of Escherichia coli can be suppressed by rho mutations (O. Reyes et al., J. Bacteriol. 126:1108-1112, 1976). We show here that this polarity can also be suppressed by ultraviolet irradiation. The effect is analogous to that already observed for polar nonsense mutations in phi X174 and S13 and suggests that ultraviolet irradiation suppression of polarity may be a general phenomenon.

Escherichia coli↗
PubMed1980

Gene K of bacteriophage phi X 174 codes for a nonessential protein.

Gene K of phi X 174, which overlaps genes A, B, and C, was found to be nonessential, although possibly beneficial for the growth of the phage. Viable mutants of gene K made less than 4% of the normal amount of K protein as judged by quantitative fluorography of sodium dodecyl sulfate-polyacrylamide gels; compared with the wild-type phi X, K mutants had an identical latent period but a two- to threefold reduction in burst size.

Bacteriophage phi X 174↗
PubMed1979

Suppression of polar effects of nonsense mutations by ultraviolet irradiation.

Nonsense mutations in capsid genes F and G of phages S13 and phi X174 decreased the expression of genes downstream. These polar effects were suppressed by ultraviolet irradiation of the host before infection. Activities of the downstream genes were restored to between 30 and 95% of their normal levels, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the viral proteins. The effect of ultraviolet irradiation may be to suppress rhodependent termination of transcription. The polarity of one mutation was poorly suppressed by ultraviolet irradiation.

Bacteriophages↗
PubMed1978

Potential for variability through multiple gene products of bacteriophage phiX174.

The small single-stranded DNA phages phiX174 and S13 produce multiple products of certain phage genes, as observed by electrophoresis on SDS-polyacrylamide slab gels. Two A protein products, two A products and four G products are observed. The multiple gene products may arise from multiple sites for initiation or termination of translation, or by protein modification. Some of the variant products may provide a substitute for heterozygosity without a concomitant increase in the size of the genome.

Chromosome Mapping↗
PubMed1978

Differential effect of hydroxyurea on a ribonucleotide reductase system.

Infection of Escherichia coli with phage T4 induces a large increase in ribonucleotide reductase activity. We show that hydroxyurea inhibits T4-induced CDP, ADP, UDP, and GDP reductase activities in vitro. Moreover, there are significant differences in the degree of inhibition of each ribonucleotide reductase activity. The reductase activities for CDP and ADP are more sensitive to hydroxyurea than those for UDP and GDP, particularly at high hydroxyurea molarities. As little as 5 x 10(-4)M hydroxyurea lowers CDP and ADP reductase activities to 25 to 30% whereas as much as 0.5 M hydroxyurea is needed to lower UDP and GDP reductase activities to 50%.

Coliphages↗
PubMed1978

Identification of lysis protein E of bacteriophage phiX174.

The product of gene E, the lysis gene of phiX174, has been identified as a distinct band in a sodium dodecyl sulfate-gel electropherogram. The position of the band is consistent with the molecular weight of 10,589 calculated from the nucleotide sequence of the gene. The band is eliminated by a nonsense mutation in gene E. It is estimated that roughly 100 to 300 molecules of E protein are made in an infected cell; this appears to be less than one-tenth the amount of protein made by gene D, in which gene E is wholly contained.

Coliphages↗
PubMed1973

Difference between functional and structural integrity of messenger RNA.

Messenger RNA molecules that are structurally stable, as measured by their ability to hybridize to DNA, may nevertheless be considerably less stable in retaining their ability to function in protein synthesis. The structure of the majority of the mRNA of phage S13 decays with a half-life of 10.6 +/- 0.5 min. In contrast, much of the function of the mRNA that is involved in synthesis of a capsid protein (product of the F gene) decays rapidly with a half-life of 1.4 +/- 0.8 min; a residual amount of function decays with a half-life of 14.0 +/- 4.0 min. The measurements were made in the presence of rifampicin, which was used to prevent the formation of new mRNA. A proposed model for the functional decay is based on the polycistronic nature of the mRNA. Degradation of the mRNA would proceed in two steps: the first step would be a fast attack at a region near the 5'-terminus of each molecule that would eliminate the function of the proximal message; the second step would be a slow attack on the remaining messenger molecule precipitating a subsequent rapid degradation of the physical structure.

Carbon Isotopes↗