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B Cabrer

Publications and source records attributed to B Cabrer.

35 records · Page 2Linked to original sources
PubMed1977

Messenger RNA methylation, translation and degradation in extracts of interferon-treated cells.

Extracts from interferon-treated, not virus infected EAT cells differ in several biochemical characteristics from extracts of untreated cells. Some of these differences are manifested only if the extracts are supplemented with ds RNA and ATP. Thus, in the extracts from interferon-treated cells these supplements activate a protein kinase and an endonuclease activity as well as an inhibitor of the translation of messenger RNA. The effect of the same supplements in extracts of untreated cells is much less pronounced. Other differences between the two types of extracts do not seem to depend on the addition of ds RNA and ATP. These include an impairment of mRNA cap methylation and an inhibition of peptide chain elongation that can be overcome by the addition of tRNA. The treatment of human (HeLa S3) cells with human interferon is manifested in the cell extract similarly to the treatment of EAT cells with mouse interferon. Studies are underway to isolate and characterize the ds RNA activated enzymes and the inhibitors and to establish how the presence of these in extracts from interferon-treated cells can account for the impairment of virus replication by interferon.

Adenosine Triphosphate↗
PubMed1976

Stoichiometry of polypeptide chain elongation.

To quantitate the amount of GTP hydrolyzed during polypeptide chain elongation, an in vitro system containing purified endogenous Escherichia coli polysomes has been developed. The polysomes are washed with 1 M NH4Cl to eliminate endogenous GTPase activities and are depleted of subunits and free ribosomes to diminish the uncoupled elongation factor G-dependent GTP hydrolysis. These polysomes, supplemented with elongation factors, aminoacyl-tRNA, and low concentrations of GTP, incorporate amino acids in their nascent peptide chains. After correcting for a background of uncoupled GTP hydrolysis, it has been found that the incorporation of each molecule of amino acid is associated with the hydrolysis of 2 molecules of GTP.

Binding Sites↗
PubMed1976

The treatment of primary atypical pneumonia with intravenous doxycycline: a report of clinical observations.

Seventeen cases of primary atypical pneumonia which were probably caused by Mycoplasma pneumoniae were studied as in-patients in hospital. All of these patients were treated with intravenous doxycycline and responded quickly to therapy. It has been shown that approximately 30-50% of the cases with primary atypical pneumonia are caused by M. pneumoniae. The remainder of the cases are caused by either viruses or possibly rickettsiae.

Adult↗
PubMed1976

Interferon, double-stranded RNA, and protein phosphorylation.

We reported earlier that the addition of double-stranded RNA and ATP increases the endonuclease activity more in an extract of Ehrlich ascites tumor cells which have been treated with an interferon preparation than in a comparable extract from control cells. We report here that the addition of double-stranded RNA to an extract from Ehrlich ascites tumor cells which have been treated with an interferon preparation [or with the interferon inducer poly(I)-poly(C)] promotes the phosphorylation by [gamma-32P]ATP of at least two proteins: P1 (molecular weight of 64,000) and P2 (molecular weight of 37,000). Double-stranded RNA also promotes the phosphorylation of at least one (i.e., P1) of these two proteins in an extract from cells which have not been treated with interferon, but the extent of phosphorylation is much smaller. Double-stranded RNA which has been degraded by RNase III, or DNA, does not promote the phosphorylation.

Adenosine Triphosphate↗
PubMed1973

The interaction of elongation factor G with N-acetylphenylalanyl transfer RNA-ribosome complexes.

N-Acetyl-Phe-tRNA, nonenzymically bound to the acceptor site of Escherichia coli ribosomes, readily undergoes translocation in the presence of elongation factor (EF)-G and GTP. The translocated N-acetyl-Phe-tRNA, bound to the ribosomal donor site, prevents further interaction of EF-G with the ribosome, for it inhibits the GTP hydrolysis that takes place in the presence of EF-G and ribosomes and it decreases the formation of either the GDP.EF-G.fusidic acid.ribosome complex or the 5'-guanylylmethylenediphosphonate.EF-G.ribosome complex. Deacylation with puromycin of the donor site-bound N-acetyl-Phe-tRNA reverses these inhibitions, even though the tRNA(Phe) moiety remains bound to the ribosme. These results suggest that ribosomes complexed with messenger RNA and peptidyl-tRNA may be restricted in their ability to interact with EF-G to that part of the elongation cycle when peptidyl-tRNA is in the acceptor site, and deacylated tRNA in the donor site. Deacylation of the donor site-bound peptidyl-tRNA associated with peptide bond formation may control the interaction of EF-G with the ribosome.

Binding Sites↗
PubMed1972

Inhibition by elongation factor EF G of aminoacyl-tRNA binding to ribosomes.

Elongation factor G (EF G), bound to ribosomes either with GMPPCP or with fusidic acid and GDP, inhibits elongation factor Tu (EF Tu)-dependent binding of Phe-tRNA on the ribosome-poly(U) complex and binding of Ala-tRNA on the initiation complex formed with RNA from bacteriophage R17; GTP hydrolysis associated with Phe-tRNA binding is also inhibited. Moreover, nonenzymic binding of Phe-tRNA at high Mg(++) concentration is completely blocked by EF G. Thus, EF G appears to bind at a site that overlaps or interacts with the ribosomal A-site.

Amino Acids↗
PubMed1971

Inhibition by siomycin and thiostrepton of both aminoacyl-tRNA and factor G binding to ribosomes.

Siomycin, a peptide antibiotic that interacts with the 50S ribosomal subunit and inhibits binding of factor G, is shown also to inhibit binding of aminoacyl-tRNA; however, it does not impair binding of fMet-tRNA and completion of the initiation complex. Moreover, unlike other inhibitors of aminoacyl-tRNA binding (tetracycline, sparsomycin, and streptogramin A), siomycin completely abolishes the GTPase activity associated with the binding of aminoacyl-tRNA catalyzed by factor T(u). A single-site interaction of siomycin appears to be responsible for its effect on both the binding of the aminoacyl-tRNA-T(u)-GTP complex and that of factor G.

Anti-Bacterial Agents↗