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Biomedical subjects

K Tagawa

Publications and source records attributed to K Tagawa.

At least 163 records · Page 9Linked to original sources
PubMed1984

Resonance Raman study of the aa3-type cytochrome oxidase of thermophilic bacterium PS3.

Resonance Raman spectra of the aa3-type cytochrome oxidase of thermophilic bacterium PS3, which has a simpler subunit composition than the mitochondrial enzymes but very similar enzymatic properties, are investigated under various conditions and compared with those of mitochondrial enzymes. The intensities of the two marker lines of reduced cytochrome a3 at 1667 and 213 cm-1 had different dependences on the incubation temperatures and pH. With regard to the incubation temperature dependence, the intensity of the 1667-cm-1 line, the peripheral CH = O stretching mode of the a3 heme, behaved in nearly the same way as that of the oxidase activity whereas the intensity of the 213-cm-1 line, the Fe-histidine stretching mode of the a3 heme, exhibited a similar dependence to that of the proton pumping activity. The 213-cm-1 line disappeared upon binding of carbon monoxide, upon raising the pH above 9.2, or after incubating above 55 degrees C. The Raman line at 1611 cm-1, which was recently suggested to probe the proton pump activity [Babcock, G.T., & Callahan, P.M. (1983) Biochemistry 22, 2314-2319], remained unaltered after incubation at 60 degrees C for 20 min despite a reduction of proton pumping activity to one-third. This argues against the proposed mechanism. The frequencies of the Raman lines were the same for the intact membrane and the isolated enzyme in the reduced state. The Raman spectra of cytochrome oxidase isolated from bacterium, yeast, and bovine heart were different in the lower frequency region below 600 cm-1 but closely alike in the higher frequency region above 1200 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Purification and properties of factors in yeast mitochondria stabilizing the F1F0-ATPase-inhibitor complex.

A previously found yeast-mitochondrial protein fraction stabilizing the inactivated complex between mitochondrial ATPase and intrinsic ATPase inhibitor (Hashimoto, T., et al. (1983) J. Biochem. 94, 715-720) was separated into two proteins by high performance liquid chromatography on a cation exchanger. The molecular weights of the factors were estimated to be 9,000 and 15,000 daltons by sodium dodecyl sulfate (SDS)-gel electrophoresis. Both factors were required to stabilize a complex of inhibitor and proton-translocating ATPase (F1F0-ATPase) either in its purified form or in mitochondrial membranes. On the other hand both factors together could not stabilize a complex of the inhibitor and F1-ATPase, suggesting that both factors act together with the F0-portion. The factors also facilitated very efficiently the binding of ATPase inhibitor to F1F0-ATPase in the presence of ATP and Mg2+. Both the 15,000 and 9,000 dalton stabilizing factors were hardly distinguishable from delta- and epsilon-subunit, respectively, on an SDS-gel electrophoregram, but immuno-diffusion assay showed that neither factor was present in the purified F1-ATPase containing the delta- and epsilon-subunit.

Adenosine Triphosphatases↗
PubMed1984

Age-related changes in the Purkinje's cells in the rat cerebellar cortex: a quantitative electron microscopic study.

The present study was undertaken to assess age-related changes in the Purkinje's cells in the rat cerebellar cortex. The cellular and nucleolar volumes and the volume percentage of lipofuscin per cytoplasma were measured in six age groups. The number of Purkinje's cells was also counted. The cellular volume of rats aged 18, 24 and 30 months decreased significantly as compared with that of 3-month-old rats. The nucleolar volume of rats aged 12, 18, 24 and 30 months decreased significantly as compared with that of 3-month-old rats. The accumulation of lipofuscin in the cytoplasma of the Purkinje's cells was observed more or less in all ages. The degree of accumulation of lipofuscin in the Purkinje's cells increased with aging. The number of Purkinje's cells at the ages of 24 and 30 months decreased significantly as compared with that of 3-month-old rats.

Aging↗
PubMed1983

pH-Induced conformational change of ATPase inhibitor from yeast mitochondria. A proton magnetic resonance study.

The ATPase inhibitor from yeast, Saccharomyces cerevisiae, was found to strongly inhibit the ATPase activity when it was preincubated in an acidic pH region. This paper describes the conformational changes of the inhibitor in the acidic pH region, as studied by 1H NMR spectroscopy. In the pH range from 7.43 to 4.48, two conformations were detected. With lowering of the pH in this pH region, one conformation increased at the expense of the other. In the two conformations, His 39 had different pKa values which were determined at 23 degrees C to be 6.08 +/- 0.04 and 5.91 +/- 0.03 from the pH-titration curves of His 39. The exchange between the two conformations was reversible with pH and the rate of the conformational change was estimated to be slower than 22 s-1 at 23 degrees C as estimated by the line-widths (7.0 Hz) of the peaks from the C2-proton of His 39 in the two conformations. The equilibrium constant between the two conformations was dependent on the temperature. From the equilibrium constants in the temperature range from 23 to 45 degrees C, the apparent delta H'a of the conformational change was calculated to be 14 kcal/mol at pH 6.95. It was confirmed by 1H NMR spectra that at pH 6.95 the structure of the inhibitor was reversible with temperature at least below 80 degrees C. The reversibility is consistent with the high thermal stability of the protein.

Hydrogen-Ion Concentration↗
PubMed1983

Cell-free synthesis of mitochondrial ATPase inhibitor precursor and its transport into yeast mitochondria.

ATPase inhibitor protein, which blocks mitochondrial ATPase activity by forming an enzyme-inhibitor complex, was found to be synthesized as a larger precursor in a cell-free translation system directed by yeast mRNA. Other protein factors, which stabilize latent ATPase by binding to the enzyme-inhibitor complex, were also found to be formed as larger precursors. The precursor of ATPase inhibitor protein was transported into isolated yeast mitochondria and was cleaved to the mature peptide in the mitochondria. Impaired mitochondria lacking phosphorylation activity could not convert the precursor to the mature form. Neither antimycin A nor oligomycin alone exhibited a marked effect on the transport-processing of the precursor by intact mitochondria. However, when antimycin A was added with oligomycin, the transport-processing was markedly inhibited. The processing was also strongly inhibited by an uncoupler, carbonylcyanide p-trifluoro-methoxyphenyl hydrazone. The inhibition by the uncoupler was not relieved by ATP added externally. It is concluded that the transport-processing of precursor proteins requires intact mitochondria with a potential difference across the inner membrane.

Animals↗
PubMed1983

Partial amino terminal sequence of the precursor of mitochondrial ATPase inhibitor protein synthesized with mRNA partially purified by gel permeation chromatography.

Messenger RNA coding mitochondrial ATPase inhibitor protein, a small peptide comprised of 63 amino acid residues, was separated from a large quantity of mRNAs of larger molecules by high speed gel permeation chromatography. Messenger RNA coding a small stabilizing factor of inactivated F1F0-ATPase complex, which is also comprised of 63 amino acids, was recovered in the same fraction as the ATPase inhibitor, whereas mRNA for a large stabilizing factor with an apparent molecular weight of 15,000 was recovered in a fraction of slightly larger molecules. ATPase inhibitor precursor labeled with various kinds of radioactive amino acids was prepared separately by cell-free translation with the purified mRNA, and the amino terminal sequence of the precursor was examined. It was demonstrated that an extra peptide of 21 amino acid residues, including 5 leucine, 4 serine, 1 glycine, and 1 methionine residues, is located at the amino terminus of the ATPase inhibitor precursor.

Amino Acid Sequence↗
PubMed1983

A stabilizing factor of yeast mitochondrial F1F0-ATPase-inhibitor complex: common amino acid sequence with yeast ATPase inhibitor and E. coli epsilon and bovine delta subunits.

The amino acid sequence of a stabilizing factor, 9,000 dalton protein, of proton-translocating ATPase (F1F0-ATPase)-inhibitor complex isolated from yeast mitochondria was established. It was highly homologous with that of yeast intrinsic ATPase inhibitor and several structural characteristics were noted. They were compared with those of E. coli epsilon and bovine delta subunits to point out the similarity among them.

Adenosine Triphosphatases↗
PubMed1983

Decrease in mitochondrial levels of adenine nucleotides and concomitant mitochondrial dysfunction in ischemic rat liver.

The process of mitochondrial dysfunction in ischemic rat liver was studied. A close correlation was found between decrease in the mitochondrial adenine nucleotide content and deterioration of oxidative phosphorylation capacity. The level of total adenine nucleotides, which was 15--20 nmol/mg protein in mitochondria isolated from normal liver, fell to 1--2 nmol/mg protein with concomitant loss of oxidative phosphorylation capacity after anoxic incubation in vitro or in vivo for 120 min. However, neither the permeability barrier to adenine nucleotides nor matrix enzymes were affected under these conditions. The loss of adenine nucleotides was ascribed to degradation of AMP to adenosine and then leakage of the latter. Conventional procedures for maintenance of oxidative phosphorylation capacity of isolated mitochondria, preservation in the cold and addition of ATP or a respiratory substrate under aerobic conditions, were very effective in maintaining the intramitochondrial levels of adenine nucleotides. Of the three species of adenine nucleotides, only AMP was ineffective in maintaining mitochondrial function; mitochondria containing more than 5 nmol of ATP plus ADP/mg protein exhibited normal activity of oxidative phosphorylation, but with less than 2 nmol they showed no activity.

Adenine Nucleotides↗
PubMed1983

Binding properties of an intrinsic ATPase inhibitor and occurrence in yeast mitochondria of a protein factor which stabilizes and facilitates the binding of the inhibitor to F1F0-ATPase.

The content of an intrinsic ATPase inhibitor in mitochondria was determined by a radioimmunoassay procedure which showed the molar ratio of the inhibitor to ATPase to be 1:1. The ratio in submitochondrial particles, where half of the enzyme was activated, was the same as that of mitochondria, indicating that the inhibitor protein has affinity for the mitochondrial membrane as well as for F1-ATPase. The inhibitor protein could be removed from the mitochondrial membrane by incubation with 0.5 M Na2SO4 and concomitantly the enzyme was fully activated. The enzyme fully activated by the salt treatment was inactivated again by the externally added ATPase inhibitor in the presence of ATP and Mg2+. The enzyme-inhibitor complex (inactive) on the mitochondrial membrane was more stable than the solubilized enzyme-inhibitor complex but gradually dissociated in the absence of ATP and Mg2+. However, in mitochondria, the enzyme activity was inhibited even in the absence of the cofactors. A protein factor stabilizing the enzyme-inhibitor complex on the mitochondrial membrane was isolated from yeast mitochondria. This factor stabilized the inhibitor complex of membrane-bound ATPase while having no effect on that of purified F1-ATPase. It also efficiently facilitated the binding of the inhibitor to membrane-bound ATPase to form the complex, which reversibly dissociated at slightly alkaline pH.

Adenosine Triphosphatases↗
PubMed1983

Evaluation and management in consultation-liaison psychiatry.

The subjects were 95 medical and surgical inpatients referred to Kyushu University Hospital Psychiatric Consultation Service. The authors studied the mental status of each referred patient and elicited some Unclassified mental status cases. It was recommended, therefore, to bring in new concepts of normal condition and polymorphous condition in dealing with those Unclassified mental status cases which are often recognized as problematic both by the patient's primary physician and the psychiatric consultant. The ordinary style Single contact consultation was also compared with the Active follow-up consultation regarding the function of psychiatric consultations. The authors confirmed that most referring physicians who were supported by the Active follow-up consultation appreciated highly the evaluating function of a psychiatric consultant.

Adolescent↗
PubMed1982

Changes in cellular levels of ATP and its catabolites in ischemic rat liver.

The cellular levels of adenine nucleotides and their metabolites in ischemic rat liver were assayed by high pressure liquid chromatography with high theoretical plate numbers. The method was sensitive enough to measure all the metabolites in about 1 mg of tissue, and to examine changes in their levels in a single liver in ischemia. In ischemia the cellular level of ATP decreased rapidly. Concomitantly there was a transitory increase in AMP, followed by its degradation to allantoin via adenosine with accumulation of all species of purine catabolites. NAD was also degraded gradually with concomitant accumulation of nicotinamide. Thus, the level of total adenine nucleotides decreased during ischemia and the amount of this decrease ws equal to the sum of the amounts of catabolites produced. The ATP level was rapidly restored on recirculation after an ischemic period of less than 15 min. However, recovery of the ATP level was depressed by prolonged ischemia and was not observed after an ischemic period of 2 h. Intermediate purine catabolites that accumulated in ischemia were also cleared during recirculation either by their removal in the blood flow or by further oxidative degradation, but they were not salvaged for reuse until the cellular level of ATP was restored. Administration of allopurinol resulted in marked accumulation of hypoxanthine in ischemic liver, but neither this drug nor chlorpromazine had any appreciable effect on recovery of the ATP level during recirculation.

Adenine Nucleotides↗
PubMed1982

Cellular level of purine compounds in ischemic gerbil brain by high performance liquid chromatography.

The cellular level of AtP and related compounds in ischemic gerbil brain was investigated by high performance liquid chromatography (HPLC). Brain samples were obtained in situ following ligation of the common carotid artery. AMP and ADP peaks in the brain extracts in the ischemic group became much larger whereas the ATP peak decreased dramatically. The most striking finding was an extensive increase of adenosine: 50-100 fold. The levels of inosine and hypoxanthine also increased greatly in typical symptomatic gerbil.

Adenine Nucleotides↗
PubMed1981

Properties of binding sites for adenine nucleotides on ATPase from yeast mitochondria.

High pressure column chromatography was applied to estimate the bound nucleotides on F1-ATPase. In this way, various species of adenine nucleotide in 0.1 to 0.3 mg of enzyme protein were well separated and estimated with a precision of about 10 nmol within 10 min. ATPase in submitochondrial particles contained 2 mol of ATP and 1 to 2 mol of ADP. The nucleotide content and binding nature of the enzyme varied at different stages of purification, but a total of four binding sites were found in enzyme preparations at all steps. Highly purified enzyme had two tight binding sites for ATP and two loose binding sites, one for ATP and one for ADP. The tight binding of ADP observed in submitochondrial particles was reconstituted by continuous supply of ATP and Mg2+ to the purified enzyme. Removal and rebinding of the nucleotides did not affect ATP-hydrolyzing activity but caused conformational changes of the enzyme, as demonstrated by measuring cold-lability and trypsin digestion. An analog of ATP, AMPP(NH)P, was found to bind to loose binding sites of the purified enzyme with 2 mol of tightly bound ATP, and to inhibit ATP-hydrolyzing activity competitively. The analog also bound to the tight sites under special conditions, protecting the enzyme against cold inactivation. During enzymatic hydrolysis of [3H]ATP, labeled ATP and ADP were both bound at the loose sites, but only slight amounts of these nucleotides were bound to the tight sites. From these results it is inferred that the loose sites are catalytic, while the tight sites are not.

Adenine Nucleotides↗