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Biomedical subjects

K Ohtsuki

Publications and source records attributed to K Ohtsuki.

At least 145 records · Page 8Linked to original sources
PubMed1980

A non-histone chromatin protein that is a specific phosphate acceptor of nuclear cAMP-independent protein kinase from mouse spleen cells.

A non-histone chromatin protein (NHCP), which is specifically phosphorylated by a nuclear cAMP-independent protein kinase from mouse spleen cells in vitro, has been purified from calf thymus chromatin. SDS-polyacrylamide gel electrophoresis shows that the molecular weight of the purified NHCP (single peptide) is 13,000. This peptide consists of 14 amino acid residues and has high serine content (17.9%). However, no methionine, proline, or half-cysteine have been detected. The NHCP is a basic protein (isoelectric point, approximately 9.0), although it has high acidic amino acid content (26.2%). This protein serves as the most effective phosphate acceptor for the kinase in vitro when compared with other chromatin proteins such as histones; the Km value of the kinase for the NHCP is 3.65 x 10(-6) M, whereas that for histone H2a (Mr = 14,000) is 1.08 x 10(-5) M. The present finding that the NHCP phosphorylation by the kinase in vitro is remarkably stimulated by double-stranded DNA but inhibited by whole histone or histone H2a suggests that the phosphorylation may be controlled by both double-stranded DNA and histone H2a.

Amino Acids↗
PubMed1980

Mouse spleen cell nuclear protein kinases and the stimulating effect of dsDNA on NHP phosphorylation by cyclic AMP-independent protein kinase in vitro.

cAMP-dependent (designated as enzyme I, about 68,000 daltons) and cAMP-independent protein kinase (designated as enzyme II, about 45,000 daltons) have been partially purified from the nuclei of mouse spleen cells. Both kinases phosphorylated calf thymus histones as well as non-histone proteins (NHP) and required Mg2+ (8 mM) or Mn2+ (2 mM) for maximal activity. NEM (0.5 mM), which is an inhibitor of SH-enzymes, inhibited the histone phosphorylating activity of enzyme II by more than 90%, whereas it inhibited the activity of enzyme I by less than 10%. Moreover, the activity of enzyme II was more sensitive to high temperature than that of enzyme I. Non-histone protein (CM-III protein) served as a more effective substrate for enzyme II than histones; the Km value for CM-III protein was 34.4 micrograms/ml whereas that for histone H2a (14,300 daltons) was 155 micrograms/ml (1.08 x 10(-5) M). CM-III protein phosphorylation by enzyme II in vitro was greatly stimulated by the addition of dsDNA, but not by single-stranded DNA or bacterial ribosomal RNA. However, the phosphorylation of CM-III protein by enzyme I was less than 50% of that of histones, and there was no stimulatory effect. SDS-gel electrophoresis showed that two distinct NHPs (about 13,000 and 19,000 daltons) prepared from calf thymus chromatin were preferentially phosphorylated by enzyme II in vitro in the presence of dsDNA. This finding suggests that these two NHPs may be specific phosphate acceptors of cAMP-independent protein kinase (enzyme II) in the nuclei of mouse spleen cells.

Animals↗
PubMed1980

The biological effect of a nonprotein component removed from neocarzinostatin (NCS).

The biological effects of both nonprotein component (NPC) and PC (protein component) from NCS have been studied in vivo and in vitro. NPC was found to not only inhibit DNA synthesis in growing cells but also induce DNA degradation in vivo and in vitro. However, neither these two biological activities of PC were detected even at a 100-times higher concentration of NPC (0.2 micrograms/ml) which inhibited 50% DNA synthesis in growing cells. NPC-induced DNA degradation in vitro was stimulated by 2-mercaptoethanol as has been reported for NCS. These results show that the NPC removed from NCS is responsible for the biological activities such as the inhibition of DNA synthesis in growing cells and the induction of DNA degradation in vivo and in vitro.

Antibiotics, Antineoplastic↗
PubMed1979

Electron microscopical and histochemical studies of outer hair cells in acoustically exposed rabbits.

After acoustic exposure, in the infranuclear region of the basal turn histochemically the lactate dehydrogenase activity increased more than normal. In the lower half of the second turn of this region, small vesicles, free ribosomes and coated vesicles decreased in number and cytoplasmic matrix become lower in electron density and lactic dehydrogenase activity decreased. Small vesicles were found to be preferentially distributed in the presynaptic side of the afferent nerve endings. Movement of these small vesicles leads to the speculation that small vesicles have close relationship to the afferent nerve endings.

Animals↗