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Biomedical subjects

A Araya

Publications and source records attributed to A Araya.

At least 55 records · Page 3Linked to original sources
PubMed1979

Reverse transcriptase mediated binding of primer tRNA to the viral genome.

A complex between tRNATrp (beef) and 35 S RNA from avian myeloblastosis virus is obtained when the mixture is preincubated in the presence of reverse transcriptase at 35 degrees C. The tRNA-RNA complex is active in initiating DNA synthesis catalyzed by reverse transcriptase. The interaction of tRNA with reverse transcriptase involves the partial unwinding of the acceptor stem of tRNA, as evidenced by nuclease digestion with RNAase T1 and micrococcal nuclease. When tRNA2Glu (coli), having a high degree of similarity with primer tRNA at the level of the acceptor stem, was used as primer for DNA synthesis, a low but significant level of incorporation was obtained, if the reaction was performed at 35 degrees C, while a high incorporation, similar to the one obtained with tRNATrp was obtained when the annealing between tRNA2Glu and 35 S RNA was performed at 80 degrees C. Our evidences point out to an important role of the viral DNA polymerase in positioning the primer on the RNA genome.

Avian Leukosis Virus↗
PubMed1979

DNA polymerases of anucleated cells. Isolation and characterization of two DNA polymerases from human platelets.

Two different DNA polymerases have been purified and characterized from human platelets. In the mitochondrial fraction a unique activity of the polymerase gamma type has been found. The same enzyme is found in the extramitochondrial supernatant. A second DNA polymerase, called 'cytoplasmic' DNA polymerase has been found in the 10000 x g supernatant of human platelets. The following properties of the latter DNA polymerase from human platelets are identical to those of DNA polymerase alpha from normal cells: DEAE-cellulose and phosphocellulose chromatography, size, thermal stability, phosphonoacetic acid and ethidium bromide inhibition. However, some of its properties, like high resistance to N-ethylmaleimide and the lack of DNA polymerization using synthetic RNA primers, are those of DNA polymerase beta.

Blood Platelets↗
PubMed1979

Amino acid sequences of the alpha and beta chains of adult hemoglobin of the European hedgehog, Erinaceus europaeus.

Globin prepared from hemoglobin of the European hedgehog (Erinaceus europaeus) was separated into alpha and beta polypeptide chains by chromatography on a CM 52 column. The S-aminoethylated alpha and beta chains were each digested with trypsin and the resulting peptides were isolated. The sequences of all the tryptic peptides were established. The ordering of these peptides in the alpha and beta chains was deduced from their homology with the primary structures of alpha and beta chains of human adult hemoglobin. Comparing the primary structures of the alpha and beta chains of adult hemoglobin of the European hedgehog thus obtained with those of adult hemoglobin of the tupai (Tupaia glis), 35 amino acids substitutions in the alpha chains and 30 in the beta chains were recognized.

Amino Acid Sequence↗
PubMed1978

[DNA polymerases in human platelets].

Human platelets have two DNA polymerases. In the mitochondrial-free cytoplasm we have found a DNA polymerase gamma and another DNA polymerase very closely related to the polymerase alpha from animal cells. In the mitochondria only the gamma activity is present.

Blood Platelets↗
PubMed1976

Studies on fish liver protein synthesis. II. Factors influencing the aminoacylation of shark liver transfer ribonucleic acid.

The influence of buffer, pH, Mg2+, ATP, Na+, K+ and temperature on the extent and rate of aminoacyl-tRNA synthesis was studied with the shark Mustelus mento liver tRNAs and aminoacyl-tRNA synthetases. The optimum pH for the aminoacylation of tRNAMet was 8.3 and for tRNAVal 7.0. For these two tRNAs the Mg2+ optimum was related to the levels of ATP required and to the pH of the reactions. It is suggested that the Mg2+ concentration required for each aminoacylation system reflects the true conditions under which the substrate for the enzyme, the MgATP2- complex, is formed. The effect of monovalent cations was also examined. Val-tRNA synthesis was slightly stimulated up to a concentration of 50 mM NaCl (KCl). Over 100 mM salt, a rapid inhibition was observed. Met-tRNA synthesis behaves differently by being stimulated over a wide range of salt concentrations.

Acetylation↗