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Biomedical subjects

A Rezee

Publications and source records attributed to A Rezee.

4 recordsLinked to original sources
PubMed1979

Purification and characterization of cloacin DF13 receptor from Enterobacter cloacae and its interaction with cloacin DF13 in vitro.

Extraction of the crude cell envelope fraction of cloacin DF13-susceptible Enterobacter cloacae strain 02 with Triton X-100 and ethylenediaminetetraacetate solubilized an outer membrane fraction which neutralized the lethal activity of cloacin DF13. A similar fraction could not be isolated from strains known to be lacking functional cloacin DF13 receptors. On this basis the isolated outer membrane fraction was assumed to contain the specific cloacin DF13 receptor. The receptor was purified to homogeneity by acetone precipitation and affinity chromatography, using cloacin DF13 as a ligand. The purified receptor was identified as a protein which consisted of a single polypeptide chain with an apparent molecular weight of 90,000 and a preponderance of acidic amino acids (pI = 5.0). The interaction of equimolar amounts of purified receptor and cloacin DF13 in vitro resulted in a complete, irreversible neutralization of the lethal activity of the bacteriocin. This interaction showed a temperature optimum at 43 degrees C but was only slightly affected by variation of the pH between 5.0 and 8.5 or by increasing the ionic strength of the incubation buffer. The receptor had no neutralizing activity towards other bacteriocins, such as colicin E1 or colicin E3.

Bacterial Proteins↗
PubMed1979

Production and excretion of cloacin DF13 by Escherichia coli harboring plasmid CloDF13.

The production and the mechanism of excretion of cloacin DF13 were investigated in noninduced and mitomycin C-induced cell cultures. A mitomycin C concentration was selected which did not cause lysis of cloacinogenic cells, but at the same time induced a maximal production of cloacin DF13. Native cloacin DF13, possessing killing activity, was first released into the cytoplasm. Shortly thereafter, the bacteriocin was transported through the cytoplasmic membrane and accumulated in the periplasm. Finally, cloacin DF13 was excreted into the culture medium. A small amount of cloacin DF13 remained associated with the cell surface. Producing cells did not become permeable for the cytoplasmic enzyme beta-galactosidase. Apparently the cloacin DF13 leaves the producing cells by an excretion process which is not similar to the mechanism proposed for bacterial secretory proteins. The processes of excretion by producing cells and of uptake by susceptible cells were also not identical because mutant cloacin DF13, which was not transported through the outer membrane into susceptible cells, was excreted like the wild-type cloacin DF13. The composition of the culture medium greatly affected production of cloacin DF13. The presence of sugars known to cause catabolite repression not only inhibited the production but also strongly reduced the excretion of cloacin DF13 into the culture medium.

Bacteriocins↗
PubMed1978

Activation of measles virus from silently infected human lymphocytes.

Lymphocytes were incubated with measles virus for 4 days in the absence of a lymphocyte stimulating agent. Such nonstimulated lymphocytes, infected with measles virus, did not express the virus antigens that are detectable by cytotoxic antibodies. Approximately 1 out of 5,000, or even fewer, of such lymphocytes produced virus as demonstrated by the infectious center assay; in the supernate only 10--100 infectious viruses per milliliter were detected. No virus structures could be observed by means of an electron microscope. However, such lymphocytes showed no reaction to phytohemagglutinin (PHA) in terms of DNA synthesis in a subsequent culture in the presence of antibodies against measles to prevent spreading of the infection to other cells. Although stimulation by PHA did not result in a significant increase in [3H]thymidine incorporation, measles virus was activated; 32 h after the addition of PHA nearly 80% of the cells were killed by measles virus antibodies and complement. The number of virus-producing cells increased to approximately 1 in 300 or more, and at 72 h the virus titer in the supernate had risen to 10(6) infectious particles per ml. This reactivation of measles virus was still obtained when PHA was added as late as 8 or more days after the initial infection.

Antigens, Surface↗