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Biomedical subjects

J Adler

Publications and source records attributed to J Adler.

At least 253 records · Page 14Linked to original sources
PubMed1977

Sensory transduction in Escherichia coli: two complementary pathways of information processing that involve methylated proteins.

The properties of two classes of behavioral mutants of Escherichia coli (called tsr and tar) are described. The mutations in these strains define two complementary pathways of information flow in bacterial chemotaxis: behavioral responses to one set of stimuli are defective in tsr mutants, while responses to a complementary set of stimuli are defective in tar mutants. A double mutant containing both genetic lesions is defective in responses to all stimuli tested. The behavioral defects are shown to correlate with alterations in the properties of a methylation reaction involved in chemotaxis. Two independent sets of methyl-accepting proteins are demonstrated in the wild type, each set functioning in one of the two pathways mentioned above. Methylation of one set of proteins is defective in tsr mutants, while methylation of the complementary set is defective in tar mutants. The double mutant shows no methylation of either set. The relationship between the genetic loci (tsr and tar) and the methyl-accepting proteins is discussed.

Bacterial Proteins↗
PubMed1976

Chemotaxis in bacteria.

Bacterial chemotaxis, the movement of motile bacteria toward or away from chemicals, was discovered nearly a century ago by Engelmann (1) and Pfeffer (2,3). The subject was actively studied for about 50 years, but then there were very few reports until quite recently. For reviews of the literature up to about 1960, see Berg (4), Weibull (5), and Ziegler (6). The present review will restrict itself to the recent work on chemotaxis in Escherichia coli and Salmonella typhimurium. Some of this is also covered in Berg's review (4), and a review by Parkinson (7) should be consulted for a more complete treatment of the genetic aspects.

Bacterial Proteins↗
PubMed1976

Change in membrane potential during bacterial chemotaxis.

To find out if there are changes in membrane potential during bacterial chemotaxis, we measured the membrane potential of Escherichia coli indirectly by use of the permeating, lipid-soluble cation triphenylmethylphosphonium. Addition of attractants or repellents to the bacteria brought about a hyperpolarizing peak (as well as additional, later changes in membrane potential). This peak was shown to be a part of the chemotactic mechanism based on the following evidence: (i) All attractants and repellents tested gave this peak while chemotactically inert chemicals did not. (ii) Mutants lacking galactose taxis failed to give the peak with galactose but did with another attractant and with repellents. (iii) Methionine, required for chemotaxis, is also required for production of this peak. (iv) A mutant in a control gene )flaI), unable to synthesize flagella and cytoplasmic membrane proteins related to motility and chemotaxis, failed to give the peak. (v) Paralyzed (mot) mutants gave little or none of the peak. Generally nonchemotactic (che) mutants, on the other hand, did give this peak. Very likely there are ion fluxes that bring about this change in membrane potential. We discuss the possible role of the mot gene product as an ion gate controlled by a methylation-demethylation process in response to attractants and repellents acting through their chemoreceptors.

Chemotaxis↗
PubMed1976

Virus-like particles from killer, neutral, and sensitive strains of Saccharomyces cerevisiae.

Procedures were developed for purification of virus-like particles (VLPs) from killer, neutral, and sensitive strains of Saccharomyces cerevisiae. Morphologically similar spherical VLPs measuring 40 nm in diameter were extracted from all three phenotypes. The particles were partially purified by high-speed centrifugation through a layer of CsCl (1.26 g/cm3) and sucrose density gradient centrifugation. Gradient-purified preparations contained three centrifugal species that sedimented at approximately 43, 102, and 162S. The 43S component is considered to be an artifact. Preparations from killer strains contained three double-stranded RNA (ds-RNA) components with molecular weights of 1.19 x 10(6), 1.29 x 10(6) and 2.54 x 10(6). VLPs from neutral and sensitive strains contained only the largest ds-RNA species. VLP preparations were subsequently separated into two major density components by CsCl equilibrium gradient centrifugation. The light component banding at 1.28 to 1.30 g/cm3 was void of nucleic acid, and the heavy component banding at 1.40 g/cm3 contained only the largest ds-RNA species.

Inclusion Bodies, Viral↗
PubMed1975

Methylation of a membrane protein involved in bacterial chemotaxis.

A protein methylation reaction involved in chemotaxis of Escherichia coli has been identified. The involvement of this reaction in chemotaxis in indicated by four lines of evidence. (a) The methylation reaction is altered in several classes of generally nonchemotactic mutants and is coreverted with the chemotaxis defects. (b) The methylation level of the protein is affected by chemotactic stimuli. (c) The transferred methyl group is derived from methionine and is labile, in accord with the known fact that chemotaxis requires a continuous supply of methionine. (d) Methylation is abnormal in various mutants having defective or missing flagella.

Bacterial Proteins↗
PubMed1975

Role of methionine in bacterial chemotaxis: requirement for tumbling and involvement in information processing.

Chemotactic responses are mediated by modulation of the frequency of tumbling. Studies with methionine auxotrophs of wild-type Escherichia coli and four mutants which tumble continuously show that methionine or one of its metabolites is involved in the tumbling process. Following removal of methionine, the wild type and two mutants, after various periods of time, became unable to tumble. The presence of constant levels of chemical attractants considerably shortened these periods in the three strains and eliminated tumbling in another mutant. This effect of attractants considerably shortened these periods in the three strains and eliminated tumbling in another mutant. This effect of attractants implies that methionine or some derivative of methionine is also involved in transducing chemical stimuli to bacterial responses.

Arsenates↗