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Biomedical subjects

J Hashimoto

Publications and source records attributed to J Hashimoto.

At least 217 records · Page 12Linked to original sources
PubMed1977

Importance of 5'-terminal blocking structure to stabilize mRNA in eukaryotic protein synthesis.

The 7-methylguanylic acid residue confronting the 5'-terminal nucleotide of mRNA through two pyrophosphate linkages was completely removed by tobacco pyrophosphatase from mRNAs of cytoplasmic polyhedrosis virus, tobacco mosaic virus (viral RNA), and globin without any scission in the inner part of the RNA chain. Protein synthesis ability in a wheat germ cell-free system was lost after this treatment of all three kinds of mRNA. The initiation complexes for protein synthesis of these three RNAs were not obtained after using tobacco phosphodiesterase-treated mRNA. On incubation of mRNA in a wheat germ extract, the mRNA lacking m7G was quickly degraded from the 5' terminus in an exonucleolytic way, whereas the intact mRNA remained stable. These results show that one of the confronting nucleotide structure's functions is to stabilize the mRNA, to prevent its degradation.

Animals↗
PubMed1977

Chemical modifications of ribonuclease U1.

In order to obtain information on the nature of the amino acid residues involved in the activity of ribonuclease U1 [EC 3.1.4.8], various chemical modifications of the enzyme were carried out. RNase U1 was inactivated by reaction with iodoacetate at pH 5.5 with concomitant incorporation of 1 carboxymethyl group per molecule of the enzyme. The residue specifically modified by iodoacetate was identified as one of the glutamic acid residues, as in the case of RNase T1. The enzyme was also inactivated extensively by reaction with iodoacetamide at pH 8.0 with the loss of about one residue each of histidine and lysine. When RNase U1 was treated with a large excess of phenylglyoxal, the enzymatic activity and binding ability toward 3'-GMP were lost, with simultaneous modification of about 1 residue of arginine. The reaction of citraconic anhydride with RNase U1 led to the loss of enzymatic activity and modification of about 1 residue of lysine. The inactivated enzyme, however, retained binding ability toward 3'-GMP. These results indicate that there are marked similarities in the active sites of RNases T1 and U1.

Amino Acids↗