Intracellular peptides of escherichia coli

Zusammenfassung Mittels Papierchromatographie und Hochspannungselektrophorese konnten in Trichloressigsäureextrakten vonE. coli 3–8 Aminosäuren enthaltende Peptide isoliert werden, in denen am häufigsten Glutaminsäure, Glycin, Cystein, Lysin, Asparagin und Alanin vorkommt.     

thiD locus ofEscherichia coli

Summary A mutant strain ofEscherichia coli K-12 lacking phosphomethylpyrimidine kinase activity was produced from the polyauxotrophic female strain, JC1552. The locus of its lesion, for which we propose the designationthiD, was mapped at about 46 min on the chromosome.     

Crystallization and properties of L-asparaginase fromEscherichia coli

Zusammenfassung L-Asparaginase ausE. coli ist bei hoher Proteinkonzentration zwischen pH 5,0 und 6,5 und geringer Ionenstärke durch Zugabe von Äthanol in der Kälte leicht kristallisierbar. Bei pH 5,0 und pH 6,5 entstehen unterschiedliche Kristallformen. Das durch Kristallisation gereinigte Enzym lässt sich bei erhöhter Temperatur inaktivieren, wobei das Produkt der Inaktivierung ebenso kristallisiert werden kann. Es zeigt das gleiche Verhalten in der Ultrazentrifuge wie das aktive Enzym.     

Action of cloxacillin and Nafcillin onEscherichia coli

Résumé Divers aspects de l'action de la cloxacilline et de la nafcilline surEscherichia coli ont été étudiés. La cloxacilline s'est montrée plus efficace que la nafcilline quand il s'agissait d'arrêter la croissance et d'amener la lyse et la formation de sphéroplastes; par contre, elle s'est montrée moins efficace que plusieurs autres pénicillines (y compris l'acide 6-aminopénicillanique) à ces égards. Ces résultats tendent à démontrer que la cloxacilline et la nafcilline possèdent un mode d'action qui est typique des pénicillines sur cet organisme.     

Elaboration of vitamin B12 byEscherichia coli

Résumé Les auteurs ont constaté l'absence de la vitamine B₁₂ dans le corps 1° deE. coli 113-3, 2° de son parent prototrophique et 3° dans la souche sauvage. Le titre de B₁₂ dans le milieu de culture s'est trouvé fortement augmenté par la méthionine, dans le cas de la souche sauvage uniquement. En ajoutant de la cyanocobalamine on a obtenu dans les trois cas une augmentation de désoxyribosides.

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This work was supported by Grants A-1800 and A-1231 from the U. S. Public Health Service and Grants-in-Aid from the Loomis Foundation, the American Cancer Society, and the Nat. Ass. for Mentel Health.     

High magnesium content ofEscherichia coli B

Summary We have found that the intracellular concentration of magnesium in exponentially growingEscherichia coli B is much higher than has been previously assumed; it is about 100 mM. Results of equilibrium dialysis suggest that nearly all of this Mg is bound, probably most of it to nucleic acids. These findings could have important consequences for the study of protein-DNA interactions and the in vitro simulation of protein biosynthesis.This research was supported by the Swiss National Science Foundation.We are most indebtet to prof. H.G. Seiler (Institute of Analytical Inorganic Chemistry, University of Base) for his extermely valuable help with atomic absorption spectrophotometry. In addition. H. Jütte and, particularly. F. Borle, have helped in the experiments which are only mentioned here and which will be published in extenso together with these authors in forthcoming papers.     

Proteases and protein degradation inEscherichia coli

InE. coli, protein degradation plays important roles in regulating the levels of specific proteins and in eliminating damaged or abnormal proteins.E. coli possess a very large number of proteolytic enzymes distributed in the cytoplasm, the inner membrane, and the periplasm, but, with few exceptions, the physiological functions of these proteases are not known. More than 90% of the protein degradation occurring in the cytoplasm is energy-dependent, but the activities of mostE. coli proteases in vitro are not energy-dependent. Two ATP-dependent proteases, Lon and Clp, are responsible for 70–80% of the energy-dependent degradation of proteins in vivo. In vitro studies with Lon and Clp indicate that both proteases directly interact with substrates for degradation. ATP functions as an allosteric effector promoting an active conformation of the proteases, and ATP hydrolysis is required for rapid catalytic turnover of peptide bond cleavage in proteins. Lon and Clp show virtually no homology at the amino acid level, and thus it appears that at least two families of ATP-dependent proteases have evolved independently.     

Antinicotinic properties of papaverine in guinea-pig taenia coli

Zusammenfassung Mit Hilfe der Saccharosetrennwand-Methode wird nachgewiesen, dass Papaverin antinikotinisch an der glatten Muskulatur (Taenia coli) des Meerschweinchens wirkt.     

Evolution of virulence factors in Shiga-toxin-producing Escherichia coli

The major demonstrated or putative virulence factors of Shiga-toxin-producing Escherichia coli (STEC) are the Shiga toxins, products of the locus of enterocyte effacement, and products encoded by the EHEC-hemolysin plasmid. Molecular analysis shows that STEC acquired the majority of these virulence factors by horizontal transfer of genetic material. In the case of Shiga toxins, the phages encoding them are probably responsible for this transfer. For the locus of enterocyte effacement, however, it is not clear how often this transfer took place and which parts of the locus were involved in this transfer. The large EHEC-hemolysin plasmid is clearly a mosaic structure, which arose from multiple recombination events with foreign DNA. Two lineages of this plasmid can be distinguished, one of which is associated with chromosomally encoded virulence factors. Despite the wealth of information available, further comparative studies are needed to decipher definitively the evolution of virulence in STEC.     

Mutagenecity in the mal regions ofEscherichia coli

Résumé L'efficacité de la nitrosoguanidine (MNG) dans différents milieux de culture et tampons a été étudiée. Les résultats obtenus montrent qu'avec le temps, la fraction de cellules survivant au traitement diminue progressivement alors que la fréquence de mutation augmente dans tous les milieux. L'activité de cet agent atteint un maximum dans le milieu DM-glucose tandis que dans le tampon TM elle est à son plus bas niveau.