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J Lucas-Lenard

Publications and source records attributed to J Lucas-Lenard.

32 records · Page 2Linked to original sources
PubMed1976

Processing of mengovirus precursor polypeptides in the presence of zinc ions and sulfhydryl compounds.

The effect of zinc ions on the post-translational cleavage of mengovirus polypeptides has been examined. The cleavage of the "A" precursor, which gives rise to the capsid proteins, was the most sensitive at concentrations of zinc chloride from 0.1 to 1.0 mM. Beta-mercaptoethanol and dithiothreitol antagonized the zinc-promoted inhibtion of clevage. Our results indicate that zinc ions interfere with the proper folding of the nascent polypeptide precursor rather than inhibit the proteases responsible for the cleavages. Thus, proper folding of mengovirus polypeptide "A" appears to be necessary for subsequent processing by proteases.

Dithiothreitol↗
PubMed1975

Studies on the in vitro synthesis of ppGpp and pppGpp.

The effect of a number of inhibitors of protein synthesis on ppGpp and pppGpp synthesis in vitro has been examined. As expected from in vivo results, chloramphenicol is without effect on this reaction. Aurintricarboxylic acid and chlortetracycline, on the other hand rapidly and specifically inhibit ppGpp synthesis. Fusidic acid in the presence of saturating amounts of EF G also inhibits the reaction completely, suggesting that an empty ribosomal acceptor site is necessary for this reaction. On the other hand, the 50-S subunit proteins L7 and L12 are not required for stringent factor activity. Ribosomes from Pseudomonas fluorescens can replace those from Escherichia coli in the complete system, while ribosomes from Ehrlich ascites cannot. A small but reproducible synthesis of ppGpp is observed when the ribosomal wash from E. coli is complemented with ribosomes from wheat germ cytoplasm.

Animals↗
PubMed1974

Fate of mRNA of L-cells infected with mengovirus.

Mengovirus infection of L-cells results in an inhibition of host protein synthesis which is detectable in vivo by a decreased rate of incorporation of radioactive amino acids into acid-insoluble material and by a concomitant reduction in polysome content. The inhibition of host protein synthesis occurs early in the infection cycle, at a time when there is little synthesis of viral proteins. In this paper the stability of polyadenylic acid [poly(A)]-containing mRNA of uninfected L-cells and cells infected with mengovirus is compared. Our results suggest that there is no increase in the rate of degradation of cellular mRNA upon virus infection. The continued integrity of host mRNA throughout infection was verified by acrylamide gel electrophoresis.

Amino Acids↗
PubMed1974

Cleavage of mengovirus polyproteins in vivo.

The synthesis of mengovirus-specific proteins in vivo was studied by labeling the viral proteins with radioactive amino acids under conditions in which host protein synthesis was almost completely inhibited. Pulse-chase experiments enabled the kinetic analysis of the cleavages of certain viral protein precursors and the formation of others. The pattern of cleavages of mengovirus precursor polypeptides is similar to that of encephalomyocarditis virus. The major difference between the two viruses seems to be in the molar concentration in which the various primary products are produced. The molar ratio of the A protein, which is the precursor of the capsid proteins, to that of the primary products F and C, is approximately 1.5 to 2.0: 1: 1. Possible explanations for the unequal appearance of the structural and nonstructural proteins are discussed.

Amino Acids↗
PubMed1969

Release of transfer RNA during peptide chain elongation.

In amino acid polymerization, the tRNA donating its peptidyl moiety to the neighboring aminoacyl-tRNA must be released from the ribosome for further growth of the polypeptide chain. It was not known at what stage of peptide elongation this tRNA is released. To study this question, we prepared ac-C(14)-Phe-H(3)-tRNA using H(3)-tRNA isolated from E. coli strain 15THU grown in the presence of H(3)-uracil, and followed the fate of the H(3)-tRNA during chain growth. Our results indicate that donor tRNA is released during the translocation step, mediated by the soluble factor G and GTP.

Carbon Isotopes↗