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Biomedical subjects

C W Tabor

Publications and source records attributed to C W Tabor.

At least 73 records · Page 4Linked to original sources
PubMed1977

Localized mutagenesis with bacteriophage Mu: method for increasing the frequency of specific bacterial mutants.

A method is described for markedly enriching a bacterial population for cells containing any given Mu insertion mutation. The method involves the transfer of a small piece of deoxyribonucleic acid from a Mu-infected Hfr donor donor strain to a suitable F- strain and a subsequent selection of those recombinant organisms that have received a Mu prophage from the donor. The method is particularly usefule for isolating mutants whose selection requires "brute-force" assay, since only a few hundred colonies have to be screened.

Coliphages↗
PubMed1977

Isolation of a metK mutant with a temperature-sensitive S-adenosylmethionine synthetase.

An Escherichia coli metK mutant, designated metK110, was isolated among spontaneous ethionine-resistant organisms selected at 42 degrees C. The S-adenosylmethionine synthetase activity of this mutant was present at lower levels than in the corresponding wild-type strain and was more labile than the wild-type enzyme when heated or dialyzed. A mixture of mutant and wild-type enzyme preparations had an activity equal to the sum of the component activities. These facts strongly suggest that the mutated gene in this strain is the structural gene for this enzyme. Genetic mapping experiments placed the metK110 mutation near or at the site of other known metK mutants (i.e., 63 min), confirming its designation as a metK mutant. A revised gene order has been established for this region, i.e., metC glc speC metK speB serA.

Chromosome Mapping↗
PubMed1976

1,4-Diaminobutane (putrescine), spermidine, and spermine.

As is evident from the above summary of the recent literature, plus many other papers not cited here, there is an extensive literature indicating the physiological significance of these amines. The most important studies can be summarized as follows. (a) Polyamines and their biosynthetic enzymes are ubiquitous. (b) Microbiological mutants have been described in which there is a definite requirement of polyamines for growth. (c) The concentration of polyamines and their biosynthesis enzymes increase when the growth rate increases. These increases usually precede or are simultaneous with increases in RNA, DNA, and protein levels. (d) Ornithine decarboxylase has a remarkably fast turnover rate in animal cells, and the level of this enzyme rapidly changes after a variety of growth stimuli. (e) Polyamines have a high affinity for nucleic acids and stabilize their secondary structure. They are found associated with DNA in bacteriophages and have a variety of stimulatory effects on DNA and RNA biosynthesis in vitro. (f) Polyamines stimulate protein synthesis in vivo and in vitro. (g) Polyamines protect spheroplasts and halophilic organisms for lysis, indicating their ability to stabilize membranes. Despite these observations, no specific mechanism has been firmly established for the action of the polyamines in vivo. It is clear that these compounds are physiologically important, however, and further work is necessary to establish the mechanism of their action.

Adenosylmethionine Decarboxylase↗
PubMed1962

STABILIZATION OF PROTOPLASTS AND SPHEROPLASTS BY SPERMINE AND OTHER POLYAMINES.

Tabor, Celia W. (National Institute of Arthritis and Metabolic Diseases, Bethesda, Md.). Stabilization of protoplasts and spheroplasts by spermine and other polyamines. J. Bacteriol. 83:1101-1111. 1962.-Spermine (10(-3)m) or spermidine prevents lysis of lysozyme-produced protoplasts of Escherichia coli W, E. coli B, and Micrococcus lysodeikticus in hypotonic media. Spheroplasts prepared by the action of penicillin are also stabilized by these concentrations of spermine and spermidine, but the protection is not as complete. Streptomycin, polylysine, and Ca(++) are also effective or partially effective stabilizers, but 1,4-diaminobutane, 1,5-diaminopentane, ornithine, Mg(++), and monovalent cations have no protective action at 10(-3)m concentration, and only a slight effect at higher concentrations. The osmotic stability conferred on protoplasts by spermine is irreversible. However, the protective effect of polyamines against lysis is not accompanied by restoration of viability to lysozyme protoplasts. There is a marked reduction in the loss of ultra-violet-absorbing material from the protoplasts to the medium when 10(-3)m spermine is present.

Journal Article↗