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Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 271 records · Page 15Linked to original sources
PubMed1977

A correlation between the secondary structure of DNA and the reactivity of adenine residues with chloroacetaldehyde.

The rate of reaction of chloroacetaldehyde (0.039 M) with the "free" adenine residue in deoxyadenosine-5'-phosphate (dAMP) at pH 6.5 has been found to be nearly equal to that at pH 4.5. Practically 100% of the adenine is converted to a fluorescent product (epsilon-adenine residue) on incubation for 60 h at 37 degrees C and pH 6.5. Of the adenine residues in "single-stranded" DNA, however, only 14% react with chloroacetaldehyde (0.039 M) under the same incubation conditions. The reaction rate of this 14% is nearly equal to that of dAMP, but the fluorescence of the product is appreciably quenched; the quantum yield is only 0.45 times that of the "free" adenine residue. In "double-helical" DNA, on the other hand, no adenine residue has been found to react with chloracetaldehyde. Possible application of these findings to structural studies of DNA is suggested.

Acetaldehyde↗
PubMed1977

Effects of ATP and ADP on hydrogen-deuterium exchange in heavy meromyosin. An examination of difference spectra.

The exchange reaction of peptide hydrogens with deuterium has been followed by measuring the decrease of the amide II band for heavy meromyosin (HMM). The difference spectra between HMM and HMM + ATP, between HMM and HMM + ADP, and between HMM + ATP and HMM + ADP have been examined as functions of time in order to detect small differences in the kinetic behavior of these different states of HMM. It has been found that, at 14 degrees C and 26 degrees C (pH 8.0), the exchange reaction is slightly slower for HMM + ATP than for HMM, and slightly slower for HMM + ADP than for HMM + ATP. This indicates that the secondary structure of HMM changes its flexibility during the ATP splitting cycle.

Adenosine Diphosphate↗
PubMed1977

Thermotropic transition in the states of proteins in sarcoplasmic reticulum vesicles.

Interaction between protein and phospholipid molecules in sarcoplasmic reticulum (SR) was studied by measurement of the conformational fluctuation of the protein using the kinetics of the hydrogen-deuterium exchange reaction. It was revealed that the state of SR ATPase undergoes a phase transition at about 18 degrees C with boundary lipids, corresponding to a discrete change in the activation energy of the Ca2+, Mg2+-ATPase reaction.

Animals↗
PubMed1977

Structural fluctuation of the polypeptide-chain elongation factor Tu. A comparison of factors from Escherichia coli and Thermus thermophilus HB8.

The kinetics of hydrogen-deuterium exhcange in the polypeptide chain elongation factor Tu (EF Tu) from Escherichia coli and that from Thermus thermophilus HB8 has been examined in aqueous solutions at various pH and temperatures by means of infrared absorption measurements. The free EF-Tu from E. Coli has a greater reaction rate at all pH values and at every temperature than that of the GTP-bound or GDP-bound EF-Tu. The free EF-Tu from T. thermophilus, on the other hand, has an alomst equal reaction rate to that of EF-Tu-GDP in the temperature range 38-55 degrees C. For the peptide NH groups belonging to a medium-labile kinetic class, a small but definite difference in the rate of exchange reaction was observed between EF-Tu-GDP and EF-Tu-GTP for both E. coli and T. thermophilus. For less labile peptide NH groups, on the other hand, the rate of the exchange reaction with EF-Tu-GDP from T. thermophilus is only slightly affected by the pH of the solution at 38 degrees C and 45 degrees C, while the rate constant(k) with E. coli EF-Tu-GDP is pH-dependent (log k oc pH). For T. thermophilus EF-Tu, heat stability measurements, kinetics of the rates of GDP and GTP dissociation, and circular dichroic measurements have also been made. The molecular basis for the thermostability of T. thermophilus EF-Tu is discussed.

Circular Dichroism↗
PubMed1976

Correlation among turnover of nucleic acids, ribonuclease activity and sporulation ability of Saccharomyces cerevisiae.

The turnover of nucleic acids and changes in ribonuclease activity during sporulation of Saccharomyces cerevisiae were studied. In the sporulating strains, 37-58% of vegatatively synthesized RNA were degraded during the sporulation process. The degree of degradation of vegetative RNA was proportional to the sporulation ability. In the non-sporulating strains, the degradation of vegetative RNA was less than 28% in the sporulation medium. Accompanied by the degradation of vegetative RNA, a ribonuclease activity increased several times during sporulation. We have found a close relation among the sporulation rate, the degree of the degradation of vegetative RNA and the increase in ribonuclease activity in the sporulation medium, using cells of which sporulation ability was repressed by changing the age or carbon source in various degrees.

Carbon↗
PubMed1976

Structure and fluctuation of a Streptomyces subtilisin inhibitor.

The kinetics of the hydrogen-deuterium exchange reaction in a subtilisin inhibitor from Streptomyces albogriseolus has been examined by infrared absorption measurement in aqueous solutions at various pH values and temperatures. In the analysis of each piece of kinetic data, it was assumed that the total 104 peptide hydrogen atoms are classified into three kinetic classes A, B1, and B2, and that the sizes of these classes are 72, 15, and 17, respectively at every pH and at every temperature examined. On the basis of the peak position determined for the amide II band in each stage of the exchange reaction, an approximate assignment was suggested of the A, B1 and B2 respectively to an unordered structure, a beta-structure,and an alpha-helical structure in the molecule. This assignment was supported by infrared absorption measurement of a film of this protein and by circular dichroic study of the solutions. On the basis of the temperature effect on the hydrogen-exchange rate constants and on the basis of ultraviolet absorption study in the higher temperature region (40 to 90 degrees C), a discussion has been made on the nature of the fluctuation of the molecular structure of this protein.

Bacterial Proteins↗
PubMed1976

Promotion of sporulation by caffeine pretreatment in Saccharomyces cerevisiae. II. Changes in ribonuclease activity during sporulation.

Changes in RNase activity during sporulation of a homothallic diploid strain of Saccharomyces cerevisiae were measured in caffeine-treated and non-treated cells. 1. In caffeine-treated cells soon after the transfer to the sporulation medium a significant increase in RNase activity was observed; in control cells the rise of RNase activity was less and started after a lag period of 5 h. The final activity of RNase activity was about twice as high in caffeine-treated cells as in control cells. 2. Increase in RNase activity during sporulation was sensitive to cycloheximide in control cells, but insensitive in caffeine-treated cells. 3. RNases from vegetative cells and from sporulating ones are different in their Km values. Relation of the changes in RNase activity to premeiotic DNA synthesis is discussed.

Caffeine↗
PubMed1976

Hydrogen-deuterium exchange in the histidine residues of bovine alpha-lactalbumin.

The proton magnetic resonance spectrum of bovine alpha-lactalbumin has been observed, and three peaks assignable to the position-2 CH protons of the three histidine rpsidues (His 32, 68, and 107) of this protein have been subjected to detailed examination. The assignments of these peaks to His 32, 68, and 107 were made on the basis of the difference in their reactivities with iodoacetic acid. The rate constants of the hydrogen-deuterium exchange reactions were found to be 8.0 X 10(-5), 2.6 X 10(-4), and 8.0 X 10(-5) min-1, respectively, at pH 8.5 and at 35 degrees, while at 62 degrees all three were found to be 0.84 approximately 1.1 X 10(-2) min-1. On the basis of these data, it has been shown that, in the native form of this protein, His 68 is the most exposed to the solvent while His 32 and His 107 are buried slightly deeper in the surface of the molecule. The fluctuation amplitudes gamma, or the effective chances of His 32, 68, and 107 to be fully exposed to the solvent, were found to be 0.4, 1.3, and 0.4, respectively.

Deuterium↗
PubMed1976

Polyamine-dependent deoxyribonuclease activity from rat-liver nuclei.

When nuclei isolated from rat liver in a low salt buffer were washed with 0.1 M NaCl solution, the supernatant showed a deoxyribonuclease (DNase) activity. The activity required Mg2+ and in addition spermine or spermidine, and its optimal pH was 7.2-7.4. The activity was higher on denatured (single stranded) DNA than on double-helical DNA. With both substrates the activity was highest at a polyamine concentration at which the DNA-polyamine complex began to precipitate. No Mg2++Ca2+ dependent DNase activity was detected in the preparation.

Animals↗