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Biomedical subjects

H Echols

Publications and source records attributed to H Echols.

107 records · Page 6Linked to original sources
PubMed1969

A factor that stimulates RNA synthesis by purified RNA polymerase.

A protein factor, partially purified from E. coli, can stimulate some 30- to 50-fold the transcription of DNA by purified RNA polymerase. Evidence is presented suggesting that this stimulatory factor (designated M factor) exerts its effect before the RNA synthesis is initiated. The M factor is prepared from a crude ribosome fraction, but it does not require the presence of ribosomes for full activity.

Centrifugation, Density Gradient↗
PubMed1966

Glucose effect and the galactose enzymes of Escherichia coli: correlation between glucose inhibition of induction and inducer transport.

Adhya, Sankar (University of Wisconsin, Madison), and Harrison Echols. Glucose effect and the galactose enzymes of Escherichia coli: correlation between glucose inhibition of induction and inducer transport. J. Bacteriol. 92:601-608. 1966.-The inhibitory effect of glucose on the induction of the enzymes required for galactose utilization ("glucose effect") was studied in Escherichia coli. Experiments on the uptake into the cell of labeled inducers (d-galactose-C(14) and d-fucose-H(3)) pointed to inhibition at the level of inducer transport as the possible primary mechanism of the glucose effect in the case of the gal enzymes. This interpretation was supported by the finding that a mutant constitutive for the lac enzymes was resistant to glucose inhibition of galactose induction of the gal enzymes; the mutant had acquired a glucose-resistant alternative transport mechanism for galactose via the constitutively synthesized galactoside permease. Further support for the transport inhibition model was provided by the finding that glucose did not substantially inhibit induction of the gal enzymes when glucose and galactose were produced intracellularly by beta-galactosidase hydrolysis of lactose, even if excess glucose was added. The inducer uptake experiments also showed that d-galactose and d-fucose probably enter the cell via different transport systems, although uptake of both compounds was inhibited by glucose.

Carbon Isotopes↗
PubMed1963

PROPERTIES OF F' STRAINS OF ESCHERICHIA COLI SUPERINFECTED WITH F-LACTOSE AND F-GALATOSE EPISOMES.

Echols, Harrison (University of Wisconsin, Madison). Properties of F' strains of Escherichia coli superinfected with F-lactose and F-galactose episomes. J. Bacteriol. 85:262-268. 1963.-A study of F' superinfection of F' strains of Escherichia coli by F Lac P and F Gal indicates that superinfecting F Lac P may achieve a stable existence along with native F Lac P in approximately 1% of the recipient F' population. The stable presence of F Gal, on the other hand, leads to a displacement or suppression of F Lac P when F Gal is used as a superinfecting agent or as the native episome. The majority of F' bacteria used as recipients neither acquire in stable form the superinfecting F-linked genes nor demonstrate gene activity immediately after attempted transfer, as judged by alkaline phosphatase synthesis directed by an F-transferred P(+) gene. This failure to show gene activity suggests that the F' bacteria which are sterile as recipients exclude transfer rather than inhibit subsequent multiplication.

Journal Article↗
PubMedDate not supplied

Mutation rate: some biological and biochemical considerations.

This article discusses ideas about the ways in which the high fidelity of DNA replication is achieved: base selection, exonucleolytic editing, and postreplicative proofreading. I also review possible mechanisms for the enhanced mutation rate associated with SOS induction. The concept of environmental control of mutation rate and other modes of genetic variation is also considered from the point of view that SOS induction is an example of "genetic revolution".

Base Composition↗