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Biomedical subjects

E Katz

Publications and source records attributed to E Katz.

At least 307 records · Page 17Linked to original sources
PubMed1969

Synthesis of vaccinia viral proteins in cytoplasmic extracts. I. Incorporation of radioactively labeled amino acids into polypeptides.

Polypeptide synthesis has been studied in cell-free systems prepared from vaccinia virus-infected and uninfected HeLa cells. Cytoplasmic extracts containing endogenous messenger ribonucleic acid were used. Amino acid incorporation into hot trichloroacetic acid-precipitable material was linear for 15 to 20 min at 37 C. The initial rate of protein synthesis was approximately 15% of the rate in intact cells. Optimal conditions for polypeptide synthesis were similar in cell-free systems prepared from infected or uninfected cells. Requirements for an energy source and Mg(++) were demonstrated. The optimal Mg(++) concentration was 4 to 5 mm. Ribonuclease, puromycin, and cycloheximide were inhibitory. The molecular weights of the polypeptides labeled in the cell-free systems, as determined by gel filtration in 5 m guanidine hydrochloride, ranged from 16,000 to above 68,000. Polyacrylamide gel electrophoresis indicated that the polypeptides labeled in cell-free extracts of uninfected and infected cells were different. The latter closely corresponded in electrophoretic mobility with the viral polypeptides made in intact, infected cells.

Amino Acids↗
PubMed1969

Synthesis of vaccinia viral proteins in cytoplasmic extracts. II. Identification of early and late viral proteins.

The synthesis of vaccinia viral proteins has been studied in a cell-free system prepared from vaccinia virus-infected HeLa cells. The radioactively labeled proteins were identified as viral proteins by immunodiffusion, disc gel electrophoresis, and disc gel-immunoelectrophoresis. The cytoplasmic extracts, obtained from infected cells at different times during viral replication, synthesized the corresponding "early" or "late" viral proteins.

Autoradiography↗
PubMed1968

Effect of structural and stereochemical methylproline isomers on actinomycin biosynthesis.

The inhibitory effect of methylprolines on actinomycin biosynthesis by Streptomyces antibioticus was studied; the order of effectiveness was 3- >4- >5-methyl-dl-proline. Cis-3-methyl-dl-proline was 14 times more active than the trans isomer. It was also found that 4- and, possibly, 5-methylproline were incorporated into the actinomycin molecule. When 4-methylproline was present, three new actinomycins, representing 50 to 60% of the antibiotic mixture, were synthesized. Growth of the organism may be stimulated at concentrations (0.1 to 1.0 mug per ml) of 3-methylproline that inhibit antibiotic formation, thus providing additional evidence for a different mechanism of actinomycin synthesis from that of protein synthesis. Azetidine-2-carboxylic acid, piperdine-2-carboxylic acid, and hydroxyproline (but not sarcosine) reversed the inhibition due to 3-methylproline.

Chromatography, Paper↗
PubMed1968

Actinomycin analogues containing pipecolic acid: relationship of structure to biological activity.

Streptomyces antibioticus synthesizes a mixture of actinomycins which differ at the "imino acid" site of the peptide chains. In the presence of exogenous pipecolic acid, several new actinomycins were synthesized and 70% of the proline in the antibiotic mixture was replaced by the analogue. Three new antibiotics (designated Pip 1alpha, Pip 1beta, and Pip 2) were isolated from culture filtrates, purified, and crystallized. The molar ratio of pipecolic acid to proline was: Pip 1alpha, 1:0; Pip 1beta, 1:1; Pip 2, 2:0. These compounds inhibited the growth and cell division of gram-positive, but not gram-negative, bacteria. The relative inhibitory activity against bacteria, Escherichia coli deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase in vitro, and RNA synthesis in Bacillus subtilis and mouse L-929 cells was: actinomycin IV = Pip 1beta > Pip 2 > Pip 1alpha. Protein synthesis in B. subtilis was less affected, and DNA synthesis was inhibited only at higher concentrations of antibiotic tested. In L cells, DNA formation was reduced less than RNA synthesis, whereas protein synthesis was not blocked under the experimental conditions employed. Kinetic studies with B. subtilis revealed that RNA synthesis was inhibited rapidly followed by an inhibition of protein synthesis. All four antibiotics markedly inhibited the replication of vaccinia virus and reovirus in tissue culture cells, but the production of poliovirus was resistant to the antibiotics. These actinomycins bind to DNA, resulting in an elevation of its T(m) and a decrease in the peak extinction of the actinomycins. The mode of action, as well as the structure-activity relationships among the actinomycins, are discussed relative to a previously proposed model of binding.

Bacillus subtilis↗