Chemotaxis and methionine metabolism in Escherichia coli

1972 ◽  
Vol 18 (5) ◽  
pp. 591-596 ◽  
Author(s):  
John B. Armstrong
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Trichloroacetic Acid ◽  
Methionine Metabolism ◽  
Methionine Biosynthesis ◽  
Normal Cells ◽  
Active Product ◽  
The Third ◽  
Soluble Compound ◽  
Low Levels

Auxotrophic strains of Escherichia coli generally are motile and chemotactic in the absence of those amino acids needed for growth. Methionine auxotrophs, however, require low levels of methionine for chemotaxis. A prototroph, grown in the presence of methionine so as to repress methionine biosynthesis, also requires methionine for chemotaxis. In the absence of methionine the bacteria are still actively motile, and thus phenotypically resemble nonchemotactic mutants.A continuous supply of methionine is necessary for a normal chemotactic response, indicating the active product is labile. Under the conditions used to demonstrate chemotaxis, the major trichloroacetic acid (TCA) soluble metabolites of methionine are spermidine, S-adenosylmethionine (SAM), and a third, as yet unidentified, compound. Spermidine is readily taken up by the bacteria, but does not replace methionine for chemotaxis. S-adenosylmethionine cannot be tested directly, as it is not taken up by normal cells. However, it is rapidly turned over and thus meets the requirement for lability. The third acid-soluble compound appears to be relatively stable metabolically.

Hymenolepis diminuta: The Microbial Fauna, Nutritional Gradients, and Physicochemical Characteristics of the Small Intestine of Uninfected and Parasitized Rats

1971 ◽  
Vol 49 (11) ◽  
pp. 972-984 ◽  
Author(s):  
D. F. Mettrick
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Small Intestine ◽  
Trichloroacetic Acid ◽  
Inverse Correlation ◽  
Physicochemical Characteristics ◽  
Hymenolepis Diminuta ◽  
Soluble Carbohydrate ◽  
Molar Ratios ◽  
Number Of Microorganisms

In uninfected rats the amount of trichloroacetic acid (TCA) soluble and insoluble carbohydrate in the small intestine declined steadily from duodenum to ileum. In rats infected with 10 16-day-old Hymenolepis diminuta these gradients were reversed and there was a 54% increase in the amount of TCA-soluble carbohydrate, and a 110% increase in the amount of glucose present in the luminal contents.In uninfected rats the amounts of TCA-soluble and -insoluble nitrogen and of total lipid in the small intestine were considerably more than in the intestine of infected rats. The differences may represent utilization by the worms of these nutrients.In parasitized rats the concentrations and molar ratios of the amino acids of the intestinal amino acid pool were significantly different (P < 0.001) in every region of the gut from those in uninfected animals.The intestinal pH of parasitized rats was lower than that in uninfected rats, and the pH gradient showed an inverse correlation with worm biomass and lactic acid distribution.The number of microorganisms present in the small intestine and colon of parasitized rats was less than half that in uninfected animals. Escherichia coli and the coliforms showed the greatest decrease in numbers. Other common aerobes were also markedly reduced in number. Anaerobic enterococci and yeasts were absent in the parasitized animals; anaerobic streptococci and micrococci were restricted to the ileum.

scholarly journals Association of nascent polypeptide with 30S ribosomal subunits

1973 ◽  
Vol 136 (4) ◽  
pp. 859-863 ◽  
Author(s):  
Michael Cannon ◽  
M. Amin A. Mirza ◽  
Margaret L. M. Anderson
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Trichloroacetic Acid ◽  
Sucrose Gradient ◽  
Gradient Centrifugation ◽  
Ribosomal Subunits ◽  
Nascent Polypeptide ◽  
Sucrose Gradient Centrifugation ◽  
Crude Extracts

1. Crude extracts of Escherichia coli were used to synthesize nascent peptides under the direction of endogenous mRNA and in the presence of radioactive amino acids. Analysis of such extracts by sucrose-gradient centrifugation in low Mg2+concentration has shown that after 2min of incubation approximately 14% of the total labelled protein recovered on the gradient, in association with whole ribosomes, sediments with 30S ribosomal subunits; this value rises to approximately 24% after 30min of incubation. The labelled protein associated with 30S ribosomal subunits is insoluble in hot trichloroacetic acid. 2. Similar results were also obtained in extracts that synthesized polypeptides under the direction of either of the synthetic polyribonucleotides poly(A) or poly(A,G,C,U). In contrast, however, analysis of crude extracts programmed in protein synthesis by poly(U) has indicated that under these conditions 30S ribosomal subunits have no associated polyphenylalanine; similarly there is little associated peptide after programming of extracts by poly(U,C).

Inhibition of the induced synthesis of protocatechuate oxygenase by o-nitrobenzoic acid

1970 ◽  
Vol 16 (7) ◽  
pp. 609-614
Author(s):  
Karen F. Montgomery ◽  
Norman N. Durham
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Trichloroacetic Acid ◽  
Protocatechuic Acid ◽  
Viable Cell ◽  
Insoluble Fraction ◽  
Nitrobenzoic Acid ◽  
Cell Counts ◽  
Oxygenase Activity

The synthesis of protocatechuate oxygenase (EC. 1.13.1.3), an inducible enzyme, by Pseudomonas fluorescens was inhibited by o-nitrobenzoic acid. The inhibitor did not alter the oxygenase activity of induced cells. Viable cell counts indicated that o-nitrobenzoic acid, in the concentrations used in these experiments, did not kill the cells. The inhibitor decreased the incorporation of L-tryptophan-14C and DL-glutamic-14C acid into the hot trichloroacetic acid insoluble fraction of the cell, but had no effect on the uptake of either radioactive amino acids or the inducer, protocatechuic acid. The synthesis of β-galactosidase by Escherichia coli was also inhibited by o-nitrobenzoic acid. The results establish that one site of o-nitrobenzoic acid inhibition is associated with protein synthesis in the cell.

scholarly journals Residue Aspartate-147 from the Third Transmembrane Region of Na+/H+ Antiporter NhaB ofVibrio alginolyticus Plays a Role in Its Activity

2001 ◽  
Vol 183 (19) ◽  
pp. 5762-5767 ◽  
Author(s):  
Tatsunosuke Nakamura ◽  
Yumiko Fujisaki ◽  
Hiromi Enomoto ◽  
Yuji Nakayama ◽  
Teruhiro Takabe ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Ph Dependence ◽  
Vibrio Alginolyticus ◽  
Transmembrane Region ◽  
Neutral Amino Acids ◽  
The Third

ABSTRACT NhaB is a bacterial Na+/H+ antiporter with unique topology. The pH dependence of NhaB from Vibrio alginolyticus differs from that of the Escherichia coli NhaB homolog. Replacement of Asp-147 with Glu made high H+ concentrations a requirement for the NhaB activity. Replacement of Asp-147 with neutral amino acids inactivated NhaB.

ADRENOCORTICAL FUNCTION IN PATIENTS WITH ACUTE SEVERE BRAIN AND PITUITARY LESION

1962 ◽  
Vol 40 (2) ◽  
pp. 254-262 ◽  
Author(s):  
H. H. Bassøe ◽  
R. Emberland ◽  
E. Glück ◽  
K. F. Støa
Keyword(s):  
Pituitary Gland ◽  
Adrenal Cortex ◽  
Artificial Ventilation ◽  
Practical Significance ◽  
Adrenocortical Function ◽  
The Third ◽  
Low Levels ◽  
Pituitary Lesion ◽  
Steroid Excretion ◽  
The Brain

ABSTRACT The steroid excretion and the plasma corticosteroids were investigated in three patients with necrosis of the brain and of the pituitary gland. The patients were kept alive by artificial ventilation. In two of the patients the neutral 17-ketosteroids and the 17-hydrocorticosteroids fell to extremely low levels. At the same time, the number of eosinophil cells showed a tendency to increase. Corticotrophin administered intravenously twice to the third patient had a stimulating effect on the adrenal cortex. The theoretical and practical significance of these findings is discussed.

Procaryotic Expression of Single-Chain Variable-Fragment (scFv) Antibodies: Secretion in L-Form Cells of Proteus mirabilis Leads to Active Product and Overcomes the Limitations of Periplasmic Expression in Escherichia coli

1998 ◽  
Vol 64 (12) ◽  
pp. 4862-4869 ◽  
Author(s):  
Jörg F. Rippmann ◽  
Michaela Klein ◽  
Christian Hoischen ◽  
Bodo Brocks ◽  
Wolfgang J. Rettig ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Proteus Mirabilis ◽  
Binding Activity ◽  
Host Cells ◽  
Heterologous Proteins ◽  
Single Chain Variable Fragment ◽  
Single Chain ◽  
E Coli ◽  
Active Product ◽  
Periplasmic Expression

ABSTRACT Recently it has been demonstrated that L-form cells ofProteus mirabilis (L VI), which lack a periplasmic compartment, can be efficiently used in the production and secretion of heterologous proteins. In search of novel expression systems for recombinant antibodies, we compared levels of single-chain variable-fragment (scFv) production in Escherichia coliJM109 and P. mirabilis L VI, which express four distinct scFvs of potential clinical interest that show differences in levels of expression and in their tendencies to form aggregates upon periplasmic expression. Production of all analyzed scFvs in E. coli was limited by the severe toxic effect of the heterologous product as indicated by inhibition of culture growth and the formation of insoluble aggregates in the periplasmic space, limiting the yield of active product. In contrast, the L-form cells exhibited nearly unlimited growth under the tested production conditions for all scFvs examined. Moreover, expression experiments with P. mirabilis L VI led to scFv concentrations in the range of 40 to 200 mg per liter of culture medium (corresponding to volume yields 33- to 160-fold higher than those with E. coli JM109), depending on the expressed antibody. In a translocation inhibition experiment the secretion of the scFv constructs was shown to be an active transport coupled to the signal cleavage. We suppose that this direct release of the newly synthesized product into a large volume of the growth medium favors folding into the native active structure. The limited aggregation of scFv observed in the P. mirabilis L VI supernatant (occurring in a first-order-kinetics manner) was found to be due to intrinsic features of the scFv and not related to the expression process of the host cells. The P. mirabilis L VI supernatant was found to be advantageous for scFv purification. A two-step chromatography procedure led to homogeneous scFv with high antigen binding activity as revealed from binding experiments with eukaryotic cells.

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