Search PubMed⌕ Search

Biomedical subjects

K Itakura

Publications and source records attributed to K Itakura.

At least 73 records · Page 4Linked to original sources
PubMed1987

NMR studies of the stable mismatch purine-thymine in the self-complementary d(CGPuAATTTCG) duplex in solution.

One- and two-dimensional nuclear Overhauser effect experiments demonstrate that a single hydrogen bond between a T imino proton and purine N3 is sufficient to hold the base pair dPu.dT in d(CGPuAATTTCG) by a Watson-Crick fashion rather than a Hoogsteen type. In addition, the dPu.dT base pair is well stacked with neighboring base pairs. The spin-lattice relaxation measurements at 30 and 35 degrees C of two decamers, d(CGPuAATTTCG) and d(CGAAATTTCG), reveal that the elimination of two single hydrogen bonds of dA.dT base pairs (due to the substitution of adenine for purine) in the sequence results in an increase in the overall imino proton exchange rate from 7 to 36 s-1 at the site of mismatch.

Base Composition↗
PubMed1987

Dissociation kinetics of 19 base paired oligonucleotide-DNA duplexes containing different single mismatched base pairs.

The dissociation kinetics of 19 base paired oligonucleotide-DNA duplex containing a various single mismatched base pair are studied on dried agarose gels. The kinetics of the dissociation are first order under our experimental conditions. The incorporation of a single mismatched base pair destabilizes the DNA duplexes to some extent, the amount depending on the nature of the mismatched base pair. G-T and G-A mismatches slightly destabilize a duplex, while A-A, T-T, C-T and C-A mismatches significantly destabilize it. The activation energy for the overall dissociation processes for these oligonucleotide-DNA duplexes containing 19 base pairs is 52 +/- 2 Kcal mol-1 as determined from the slope of Arrhenius plot.

Base Composition↗
PubMed1986

Single radial immunodiffusion of serum apolipoproteins C-II, C-III and E--pretreatment of samples with surfactant.

An assay of apolipoproteins (Apo) C-II, C-III and E in human sera by single radial immunodiffusion (SRID) is described. The procedure involves pretreatment of the serum sample with surfactant to facilitate diffusion of very low density lipoproteins in agarose. This allowed measurement of apolipoproteins in lipidemic sera by SRID in agarose gel. The intraplate coefficient of variation was less than 2.5%, and the interplate coefficient of variation, less than 3.0%. Correlation with double-antibody radioimmunoassay produced the following coefficients of correlation: gamma = 0.9931 (n = 17) for Apo C-II, gamma = 0.9221 (n = 33) for Apo C-III, and gamma = 0.9340 (n = 17) for Apo E.

Apolipoprotein C-II↗
PubMed1986

Synthesis and properties of oligonucleotides containing 2'-deoxynebularine and 2'-deoxyxanthosine.

The preparation of synthetic oligonucleotides containing 2'-deoxynebularine (dN) and 2'-deoxyxanthosine (dX) is described. The thermal stabilities of duplexes containing dX, dN, and 2'-deoxyinosine (dI) base-paired with the four natural bases have been measured. Xanthine base pairs have stabilities at pH 5.5 that are similar to those of dI-containing duplexes at neutral pH. When xanthine is paired with adenine or cytosine an unusual stabilization of the duplex structure is observed at acid pH. Incorporation of base mispairs opposite template xanthine sites were measured using Drosophila DNA polymerase alpha. The relative nucleoside incorporation rates are in the order: T greater than C much greater than A approximately equal to G. These rates do not correlate with relative thermodynamic stabilities of base mispairs with xanthine obtained from Tm measurements: T greater than G greater than A approximately equal to C. We suggest that DNA polymerase misinsertion rates are greatest when the base mispair can be formed in accordance with Watson-Crick as opposed to other base pairing geometries even though other geometries, e.g. wobble, may result in a more stable final DNA product.

Chemical Phenomena↗
PubMed1986

Cloning of Drosophila choline acetyltransferase cDNA.

Choline acetyltransferase (EC 2.3.1.6) is the biosynthetic enzyme for the neurotransmitter acetylcholine. To isolate choline acetyltransferase cDNA clones, a cDNA library was constructed from poly(A)+ RNA of Drosophila melanogaster heads, these being one of the richest known sources of the enzyme. By screening the cDNA library with a mixture of three different monoclonal antibodies to Drosophila choline acetyltransferase, we isolated 14 positive clones. Only 1 of these clones was identified to be a Drosophila choline acetyltransferase cDNA clone based on the following evidence. (i) The amino acid sequence deduced from the nucleotide sequence of the cDNA insert completely corresponded to that of several tryptic peptides from choline acetyltransferase. (ii) The cDNA insert hybridized specifically to only the region on Drosophila polytene chromosomes that had been identified as the site of the choline acetyltransferase (Cha) gene by cytogenetic analysis. The cDNA insert consisted of a coding region 2190 nucleotides long, a 3'-noncoding region 284 nucleotides long, and EcoRI linkers. RNA analysis of Drosophila head poly(A)+ RNA with the cDNA insert as a probe showed the choline acetyltransferase mRNA to be approximately equal to 4700 nucleotides long.

Amino Acid Sequence↗
PubMed1986

Pharmacokinetics of SCE-1141, a stereoisomer of cefmenoxime, in rats.

The pharmacokinetic properties of SCE-1141, an anti stereoisomer of cefmenoxime, were compared with those of cefmenoxime. SCE-1141 levels in plasma and tissues peaked at 30 min after the intramuscular administration of 20 mg/kg; the plasma level declined with a half-life of about 18 min. The area under the concentration-time curve in plasma and the half-life after intravenous administration were similar to those after intramuscular administration. SCE-1141 was distributed at high concentrations in the liver and kidney of normal rats, and at lower concentrations in the liver of rats with acute liver impairment. SCE-1141 levels in plasma and tissues, except liver, were lower than those of cefmenoxime. The 24-h biliary and urinary excretions of SCE-1141 were 73% and 26% of the dose, respectively; these were significantly different from those of cefmenoxime: 33% in bile and 55% in urine. In rats with acute liver impairment, the biliary excretion of SCE-1141 was decreased, and the urinary excretion increased.

Animals↗
PubMed1986

Induction of heat shock gene expression without heat shock by hepatocarcinogens and during hepatic regeneration in rat liver.

We investigated the expression of the rat hepatic heat-shock protein (hsp) genes under the influence of hepatocarcinogens and during hepatic regeneration. This was undertaken because of the inducibility of the heat-shock response in rat liver and because heat-shock genes can be expressed with or without heat shock in various cell states in a developmentally regulated manner. We found that acute administration of hepatocarcinogens to rats induced an increased hsp gene transcription in a time- and dose-dependent manner. Chronic exposure of rats to complete hepatocarcinogens induced increased levels of mainly Mr 83,000 heat-shock protein gene transcription and, to a lesser extent, Mr 70,000 heat-shock protein. However, the tumor promoter phenobarbital did not induce increased hsp gene expression. Increased levels of both Mr 83,000 heat-shock protein and Mr 70,000 heat-shock protein gene transcription were found during hepatic regeneration. Thus, increased hsp gene transcription, which correlated with increased heat-shock protein synthesis, was observed under the acute and chronic influence of hepatocarcinogens and during normal hepatic proliferation. These results are similar to those observed for c-H-ras and c-myc expression in rat liver, and they suggest that a coordinate expression of these three genes may occur in hepatic regeneration and in the early stages of experimental chemical hepatocarcinogenesis.

2-Acetylaminofluorene↗
PubMed1985

Conformation, dynamics, and structural transitions of the TATA box region of self-complementary d[(C-G)n-T-A-T-A-(C-G)n] duplexes in solution.

Structural and kinetic features of the TATA box located in the center of the alternating self-complementary d(C-G-C-G-T-A-T-A-C-G-C-G) duplex (TATA 12-mer) and d(C-G-C-G-C-G-T-A-T-A-C-G-C-G-C-G) duplex (TATA 16-mer) have been probed by high-resolution proton and phosphorus NMR spectroscopy in aqueous solution. The imino exchangeable Watson-Crick protons and the nonexchangeable base protons in the TATA box of the TATA 12-mer and TATA 16-mer duplexes have been assigned from intra and inter base pair nuclear Overhauser effect (NOE) measurements. Imino proton line-width and hydrogen exchange saturation recovery measurements demonstrate that the dA X dT base pairs in the TATA box located in the center of the TATA 12-mer and TATA 16-mer duplexes are kinetically more labile than flanking dG X dC base pairs. The proton and phosphorus NMR parameters of the TATA 12-mer monitor a cooperative premelting transition in the TATA box prior to the onset of the melting transition to unstacked strands. Phosphorus NMR studies have been unable to detect any indication of a right-handed B DNA to a left-handed Z DNA transition for the TATA 12-mer duplex in saturated NaCl solution. By contrast, we do detect the onset of the B to Z transition for the TATA 16-mer in saturated NaCl solution. Proton and phosphorus NMR studies demonstrate formation of a loop conformation with chain reversal at the TATA segment for the TATA 12-mer and TATA 16-mer duplexes on lowering the DNA and counterion concentration. The imino protons (10-11 ppm) and phosphorus resonances (3.5-4.0 ppm; 4.5-5.0 ppm) of the loop segment fall in spectral windows well resolved from the corresponding markers in fully paired segments so tha it should be possible to identify loops in longer DNA helixes. The equilibrium between the loop and fully paired duplex conformations of the TATA 12-mer and TATA 16-mer is shifted toward the latter on addition of moderate salt.

Base Sequence↗