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Biomedical subjects

E Katz

Publications and source records attributed to E Katz.

At least 289 records · Page 16Linked to original sources
PubMed1973

Synthesis of vaccinia virus polypeptides in the presence of isatin-beta-thiosemicarbazone.

Isatin-beta-thiosemicarbazone (IBT) at a concentration of 14 muM inhibited the multiplication of vaccinia virus in HeLa cells. For the first 3 h after infection, viral deoxyribonucleic acid (DNA) was synthesized in the presence of IBT at the same rate as in the control culture; the replication rate declined at a later stage. The DNA failed to be coated with proteins and to become resistant to deoxyribonuclease unless IBT was removed. "Early" and "late" viral polypeptides were formed in the presence of IBT, as revealed by polyacrylamide gel electrophoresis. The formation from precursor of a core polypeptide, a reaction blocked by rifampin, was not affected by IBT. Therefore, it is suggested that a maturation step later than the one blocked by rifampin is involved in the inhibition of vaccinia virus by IBT.

DNA, Viral↗
PubMed1972

Regulation of secondary metabolite biosynthesis: catabolite repression of phenoxazinone synthase and actinomycin formation by glucose.

Synthesis of the secondary metabolite, actinomycin, and the enzyme, phenoxazinone synthase, involved in the biosynthesis of the antibiotic, were shown to be under severe catabolite repression by glucose. Of a variety of hexoses and carbon compounds examined, glucose, and to a lesser extent, mannose, proved to be the most repressive for enzyme synthesis. The repression by glucose was most evident before production of the antibiotic. In a chemically defined medium suitable for actinomycin production, synthesis of phenoxazinone synthase began at the time the glucose (0.1%) supply was depleted. Soon after, antibiotic synthesis was initiated. Galactose, the major carbon source for growth and antibiotic synthesis, was not utilized until the glucose was consumed. Generally, carbon compounds which supported a rapid rate of growth were most effective in producing catabolite repression.

Bacterial Proteins↗
PubMed1970

Formation of a vaccinia virus structural polypeptide from a higher molecular weight precursor: inhibition by rifampicin.

A vaccinia virus core polypeptide, with a molecular weight of 76,000 and a relative deficiency in tryptophan, was shown by pulse-chase experiments to form from a precursor. The latter may be a rapidly labeled, 125,000-molecular weight, tryptophan-deficient, virus-induced polypeptide, which diminished in quantity during the chase period and was barely detectable after two to three hours. Rifampicin completely prevented the formation of the core polypeptide without inhibiting the synthesis of the precursor. A rifampicin-resistant vaccinia mutant was used to demonstrate the specificity of this effect. The sequence of events after the removal of the drug suggested that cleavage of the precursor occurs during the formation of the virus core. Rifampicin appears to act by interrupting earlier maturational events which precede the formation of the core polypeptide.

Autoradiography↗
PubMed1970

Vaccinia virus structural polypeptide derived from a high-molecular-weight precursor: formation and integration into virus particles.

Polypeptide 4a, a major vaccinia structural polypeptide which was previously shown to form from a high-molecular-weight precursor is made after the period of viral deoxyribonucleic acid (DNA) synthesis. Pulse-chase experiments demonstrated that a period of 1 to 2 hr is required for a 50% conversion of precursor to product. The rates of incorporation of polypeptides into virus particles were examined. The kinetics of incorporation of labeled 4a and other major structural polypeptides into virus particles were similar, despite the additional time required for the formation of 4a from its precursor. Furthermore, 4a was present exclusively in a particulate form at all times examined. Both observations suggested that cleavage of the precursor occurs after, or immediately prior to, association with developing virus particles. Polypeptide P4a was previously identified as the probable precursor of 4a and is not ordinarily found in detectable amounts in virus particles. Under conditions in which breakdown of P4a was inhibited by adding rifampin or amino acid analogues after the period of viral DNA synthesis, isolated virus particles contained significant amounts of this polypeptide. Further analysis showed that P4a was localized within the virus core, which is also the site of 4a. Synchronization of virus assembly after the removal of rifampin was shown to be useful for studying the integration of polypeptides into a particulate fraction of the cytoplasm.

Acrylates↗