Search PubMed⌕ Search

Biomedical subjects

K Ogata

Publications and source records attributed to K Ogata.

At least 577 records · Page 32Linked to original sources
PubMed1976

Ovalbumin synthesis in a homologous cell-free system prepared from hen's oviduct.

Hen's oviduct polysomes are present in the precipitates prepared from the oviduct homogenates by low-speed centrifugation, in constrast other eukaryotic polysomes. The polysomes possessed synthesizing activity for ovalbumin. The amount of the released form of ovalbumin (soluble ovalbumin) synthesized in cell-free system A or B, consisting of the cell sap and the total ribosomal fraction or the polysomes, respectively, was about a half of that bound to the polysomes (nascent ovalbumin). The amount of soluble ovalbumin synthesized in cell-free system C, consisting of the pH 5 fraction and the polysomes, was only about 5% of that of nascnet ovalbumin. These results indicate that factors required to release nascent ovalbumin from polysomes are present in the pH 5 supernatant fraction. The soluble and nascent ovalbumins, which were purified by chromatography on a CM-cellulose column and by the use of antiovalbumin antiserum, respectively, seemed to be elongation products the initiations of which were supposed to occur in the oviducts before preparation of the cell-free system. The initiated chains in vitro were found to exist as nascent peptides bound to polysomes. Thus, the cell-free systems prepared in the present study lacked the ability to complete initiated peptide chains. The soluble ovalbumin synthesized in the cell-free systems was indentical with ovalbumin A1 containing two residues of phosphates, which was crystallized from hen's egg-white and was different soluble ovalbumin devoid of the prosthetic group (ovalbumin A3) prepared in the oviduct minces. This result suggests that an enzyme necessary for incorporation of the phosphate is present in the cell sap.

Adenosine Triphosphate↗
PubMed1976

Biological process of carbohydrate attachment to ovalbumin.

Dithiothreitol or glutathione, essential for amino acid incorporation into polypeptides in cell-free systems, inhibited glucosamine incorporation into ovalbumin, a glycoprotein containing about three residues of N-acetylucosamine and about five residues of mannose. However, the thiol was necessary for mannose incorporation into ovalbumin in cell-free system prepared from hen's oviducts. The two monosaccharides were incorporated into soluble ovalbumin (intracellular ovalbumin released from the polysomes, corresponding to ovalbumin A3 which contains no phosphate and probably no carbohydrate) present in cell sap which was prepared from homogenates of minced oviducts by ultracentrifugation. It was difficult to study the incorporation of the carbohydrates into ovalbumin in connection with synthesis of the protein using the crude cell-free system. The incorporation of glucosamine and mannose into various forms of ovalbumin was therefore studied using minced oviducts. It was concluded from the incorporation of the two radioactive monsaccharides and of amino acids into the extracellular, soluble and nascent protein fractions that all the carbohydrate moieties were not incorporated into the growing polypeptides bound to polysomes, but were incorporated into ovalbumin molecules released from polysomes after synthesis had been completed.

Acetylglucosamine↗
PubMed1976

Synthesis of ribosomal structural proteins by postmitochondrial supernatant from regenerating rat liver.

1. When the postmitochondrial supernatant (PM-supernatant) from regenerating rat liver was incubated with [3H]methionine, the incorporation of [3H]methinoine into the N-terminal residues of nascent peptides on ribosomes was observed. This incorporation was sensitive to a low cocentration (2X10(-6) M) of pactamycin. The results suggest that PM-supernatant has low but definite activity for the initiation of nascent protein synthesis. Polysomes and cell sap from regenerating rat liver showed negligible pactamycin-sensitive incorporation of [3H]methionine into N-terminal, residues of nascent peptides. 2. PM-supernatant from regenerating rat liver was incubated with [35S]methionine in the complete reaction mixture. After addition of ribosomal proteins labelled with [3H]methionine in vivo, ribosomal structural proteins were prepared from the incubation mixture by acetic acid extraction, CM-cellulose column chromatography, Sephadex G-200 gel filtration and finally by two-dimensional acrylamide gel electrophoresis. Incorporation was observed in the greater part of ribosomal proteins on the two dimensional gel. From the 35S-to-3H ratios of ribsomal protein fractions during the purification procedures, it appeared that the incorporation of labelled methionine into the ribosomal proteins by PM-supernatant was about 3% of that into the total proteins. When [3H]leucine was used, the values were about 4% in the same cell-free system and 5 to 6% in in vivo labelling. The results indicate that ribosomal proteins are synthesized with high efficiency by PM-supernatant from regenerating rat liver.

Animals↗
PubMed1976

A butyrylcholinesterase inhibitor produced by Penicillium sp. no. C-81 and its identity with mycelianamide.

A screening aimed at obtaining a cholinesterase inhibitor of microbial origin was carried out using Pseudomonas butyrylcholinesterase. A mycelium-extract of a fungus strain, belonging to the genus Penicillium, was found to produce such an enzyme inhibitor. The inhibitor was purified and crystallized as colorless leaflets. From physical and chemical studies, the inhibitor was identified as being identical with an antibiotic, mycelianamide, though this compound was not known to have enzyme inhibitor activity. The kinetics of the inhibition of Pseudomonas butyrylcholinesterase were also studied. Horse serum cholinesterase and hog liver carboxylesterase were also inhibited by the isolated Penicillium C-81 inhibitor, but lipase and acetylcholinesterase were not.

Animals↗
PubMed1975

Preferential biosynthesis of ribosomal structural proteins by free and loosely bound polysomes from regenerating rat liver.

Homologous cell-free systems were prepared using free, total bound, tightly bound or KCl-sensitive loosely bound (KCl-sensitive) polysomes from regenerating rat liver. [14C]Leucine was incubated with one kind of polysomes and [3H]leucine with another kind. The reaction mixtures were then combined, and ribosomal structural proteins were purified as described previously [4], using two-dimensional polyacrylamide gel electrophoresis as the final step [5]. The 3H to 14C ratios of the purified fractions were estimated to compare the activities of the two kinds of polysomes for biosynthesis of ribosomal structural proteins. The following results were obtained: (1) The activity of free polysomes for biosynthesis of ribosomal structural proteins was about 3.6 or 2.4 times higher than that of total bound polysomes in two experiments in which 14C and 3H labeling was reversed. The radioactivities incorporated by free polysomes into most of the proteins separated on two-dimensional gel were found to be definitely higher than those in the surrounding areas, suggesting that most of the ribosomal structural proteins were synthesized by free polysomes. The activity of free polysomes for biosynthesis of ribosomal structural proteins was about 7 times higher than that of tightly bound polysomes, which were prepared by washing the microsomal membrane fraction with 0.5 M KCl. The radioactivities incorporated by tightly bound polysomes into the proteins separated on two-dimensional gel were only slightly higher than those in the surrounding areas, indicating that these polysomes had very low synthetic activity. (2) Preferential synthesis of histones by free polysomes was also shown using the same procedures. (3) KCl-sensitive polysomes which were released by washing the microsomal membrane fraction with 0.5 M KCl, were shown to have definitely higher activity than tightly bound polysomes for biosynthesis of ribosomal structural proteins. (4) From these results, it is concluded that most of the ribosomal structural proteins are preferentially synthesized by free and KCl-sensitive polysomes in regenerating rat liver.

Animals↗
PubMed1975

Studies on structural proteins of the rat liver ribosomes. I. Molecular wights of the proteins of large and small subunits.

Structural proteins of active 60-S and 40-S subunits of rat liver ribosomes were analysed by two-dimensional polyacrylamide gel electrophoresis. 35 and 29 spots were shown on two-dimensional gel electrophoresis of proteins from large and small subunits, respectively. It was noted that the migration distances of stained proteins with Amido black 10B remained unchanged in the following sodium dodecyl sulfate-acrylamide gel electrophoresis, although some minor degradation and/or aggregation products were observed in the case of several ribosomal proteins, especially of those with high molecular weights. This finding made it possible to measure the molecular weight of each ribosomal protein in the spot on two-dimensional gel electrophoresis by following sodium dodecyl sulfate-acrylamide gel electrophoresis. The molecular weights of the protein components of two liver ribosomal subunits were determined by this 'three-dimensional' polyacrylamide gel electrophoresis. The molecular weights of proteins of 40-S subunits ranged from 10 000 to 38 000 and the number average molecular weight was 23 000. The molecular weights of proteins of 60-S subunits ranged from 10 000 to 60 000 and the number average molecular weight was 23 900.

Animals↗
PubMed1975

Differences between the protein moieties of active subunits and EDTA-treated subunits of rat liver ribosomes with specific references to a 5 S rRNA - protein complex.

When active 40 S subunits of rat liver ribosomes were treated with EDTA, the conversion of 40 S subunits to 30 S subunits occurred with partial release of 13 kinds of proteins out of 29 kinds of 40 S proteins. Buy contrast, 60 S subunits completely lost one protein (L3) by EDTA-treatment with concomitant release of the fraction sedimenting at about 7 S (7 S fraction). It was found that the 7 S fraction contained 5 S ribosomal RNA as well as L3 protein having a molecular weight of 38,000. Buoyant density in CsCl of the 7 S fraction was 1.60 g/cm3, suggesting that this fraction consisted of RNA and protein at an approximately equal ratio on a weight basis. These findings, taken together with the molecular weights of 5 S rRNA (40,000) and L3 protein, may indicate that the 5 S ribosomal RNA - protein complex from rat liver 60 S subunits consists of one molecule of 5S ribosomal RNA and one molecule of L3 protein.

Animals↗
PubMed1975

Purification and properties of acylamino acid-releasing enzyme from rat liver.

An enzyme that releases acylamino acid from amino terminal acylated peptides and proteins has been isolated from rat liver in a highly purified form bya six-step procedure comprising extraction from liver homogenate, ammonium-sulfate fractionation, heat treatment, chromatography on columns of DEAE-cellulose and hydroxylapatite and gel filtration on a Sepharose 6B column. About 1,500-fold purification was achieved from the liver homogenate. The purified enzyme preparation showed a single band on polyacrylamide gel disc electrophoresis. The enzyme specifically released acylamino acids from several amino terminal acylated peptides and proteins with different rates of hydrolysis depending on the acyl groups, terminal amino acid sequences and tertiary structure of the acyl protein substrates. The present enzyme may be useful for the removal of the N-terminal acylamino acid from some N-terminal blocked peptides and proteins in amino acid sequence analysis. The molecular weight of the purified enzyme was estimated to be 360,000-420,000 by gel filtration and sucrose density gradient ultracentifugation. Disc electrophoresis of the acylamino acid-releasing enzyme on SDS-polyacrylamide gel suggested that the enzyme consisted of five or six identical subunits having a subunit weight of about 75,000. The N-terminal residue of the subunit, which consisted of a single polypeptide chain, was glycine. Other properties of the enzyme, including isoelectric point, the effects of metal ions and several chemical reagents on the enzyme activity, pH optimum, and amino acid composition were also examined.

Acylation↗
PubMed1975

The response of the right ventricle to experimentally induced pulmonary artery obstruction.

Banding of the main pulmonary artery was undertaken in 11 litter-mate puppies and 8 young adult beagle dogs to study the response of the right ventricle to pressure loading. Five puppies and 3 young adult dogs acted as controls, undergoing sham surgical procedures without pulmonary artery banding. In one banded puppy and one banded young adult dog, adequate banding was not achieved and each was subsequently considered with its respective control group. A trans-band gradient of 15 mm Hg or greater was deemed a successful banding procedure. Banded puppies showed an increase in the trans-band pressure gradient in the year following surgery whereas young adult dogs showed a fall in the gradient, despite satisfactory banding as shown by cardiac catheterization 14 days after surgery. Cardiac muscle analyses indicated that the right ventricle of puppies responded to pulmonary banding by an increase in total organ weight, total tissue protein, DNA and RNA without altering the protein/DNA and RNA/DNA ratios. By contrast, young adult dogs showed only slight and insignificant increases in the protein/DNA and RNA/DNA ratios. Thus the response of the right ventricle to pulmonary artery banding in puppies is hyperplastic in nature, while in young adult animals the response to a similar stress load is with mild muscular hypertrophy and dilatation. This differential cellular response to the same stimulus based on the age of the organism is another demonstration of the principle that growth responses in the young involve cellular proliferation while those in the adult consist primarily of cell enlargement. It is, therefore, perhaps erroneous to refer to cardiac enlargement in newborns and infants as cardiac hypertrophy.

Animals↗