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R M Teather

Publications and source records attributed to R M Teather.

42 records · Page 3Linked to original sources
PubMed1977

Functional symmetry of the beta-galactoside carrier in Escherichia coli.

Cytoplasmic membrane vesicles with either normal or inverted orientation were prepared from Escherichia coli. The lactose transport activity of these vesicle preparations was compared. The parameters measured were net efflux, counterflux, and K+/valinomycin-induced active uptake of lactose. With membrane vesicles derived from both wild-type and cytochrome-deficient strains the right-side-out and inverted membrane preparations showed similar rates of lactose flux in all assays. According to these criteria, the activity of the beta-galactoside transport protein is inherently symmetrical. One major difference was observed between the native and inverted vesicle preparations: the inverted vesicles had approximately twice the specific activity of native vesicles in the counterflux and K+/valinomycin-induced uptake assays. This difference can be largely ascribed to the presence in the normal vesicle preparation of vesicles with a high passive permeability to lactose. Such vesicles are apparently absent from the inverted vesicle preparations.

Biological Transport, Active↗
PubMed1976

Membrane hybridization by centrifugation analysed by lipid phase transitions and reconstitution of NADH-oxidase-activity.

A procedure is described to hybridize cytoplasmic membranes of Escherichia coli. The method involves high-speed contrifugation of two different vesicle preparations at 37 degrees C in the presence of cations such as spermine or Mg2+. The occurrence of hybridization is shown by the following experiments. Firstly, formation of a mixed lipis phase starting from two membranes having a different hydrocarbon chain composition in their phospholipids. Secondly, formation of a hybrid membrane having an intermediate lipid to protein ratio from two membrane fractions having different lipid to protein ratios. Thirdly, reconstitution of NADH oxidase activity by hybridization of two membrane fractions, one lacking active cytochromes and the other being deficient in quinones. It is proposed that hybridization occurs by fusion of vesicles during the tight association of collapsed vesicles under high centrifugal forces. This interpretation is supported by electron microscopy of the membrane pellets after centrifugation. However, lipid transfer as the mechanism of hybridization cannot be excluded and attempts to reconstitute active galactoside transport by complementation of beta-galactoside transport-deficient membranes and cytochrome-deficient membranes have been unsuccessful.

Calcium↗
PubMed1974

Quantal behavior of a diffusible factor which initiates septum formation at potential division sites in Escherichia coli.

Analysis of nucleated cell size in a minicell-producing strain of Escherichia coli and in its parental strain shows that the two distributions are considerably different. A model is proposed to account for this difference. The model states that: (i) in the mutant population, the cell poles are available as potential division sites in addition to the normally located division sites; (ii) the probability of a division occurring at any of the potential division sites is equal; and (iii) only enough "division factor" arises at each unit cell doubling to permit a single division. This factor is utilized entirely in the formation of a single septum. Thus, the occurrence of a polar division with the production of an anucleate minicell (which occurs only in the mutant strain) prevents the occurrence of a non-polar division, with the result that the average nucleated cell length is increased in minicell-producing strains. The model has been used to construct a theoretical population, and a number of parameters of the real and theoretical populations have been compared. The two populations are very similar in all of the parameters measured.

Cell Division↗