Requirement of the core structure of a complex-type glycopeptide for the binding to immobilized lentil- and pea-lectins

Structural requirements for the binding of oligosaccharides and glycopeptides to immobilized lentil- and pea-lectins were investigated by use of radioactively-labeled glycopeptides and oligosaccharides. The results indicate that an intact 2- acetamido-2-deoxy-β-d-glucopyranosyl residue at the reducing end of a complex-type oligosaccharide is essential for high-affinity binding to lentil lectin-Sepharose but not to concanavalin A-Sepharose and that an asparagine residue is required for the binding of a complex-type glycopeptide to pea lectin-Sepharose. In addition, interaction of a complex-type oligosaccharide with lentil lectin-Sepharose was enhanced by exposure of nonreducing, terminal 2-acetamido-2-deoxy-β-d-glucopyranosyl groups, whereas interaction with pea lectin-Sepharose was enhanced only after exposure of nonreducing, terminal α-d-mannopyranosyl groups.     

Glutamyl-tRNA synthetase from Thermus thermophilus HB8. Molecular cloning of the gltX gene and crystallization of the overproduced protein.

The gene for the Glu-tRNA synthetase from an extreme thermophile, Thermus thermophilus HB8, was isolated using a synthetic oligonucleotide probe coding for the N-terminal amino acid sequence of Glu-tRNA synthetase. Nucleotide-sequence analysis revealed an open reading frame coding for a protein composed of 468 amino acid residues (Mr 53,901). Codon usage in the T. thermophilus Glu-tRNA synthetase gene was in fact similar to the characteristic usages in the genes for proteins from bacteria of genus Thermus: the G + C content in the third position of the codons was as high as 94%. In contrast, the amino acid sequence of T. thermophilus Glu-tRNA synthetase showed high similarity with bacterial Glu-tRNA synthetases (35-45% identity); the sequences of the binding sites for ATP and for the 3' terminus of tRNA(Glu) are highly conserved. The Glu-tRNA synthetase gene was efficiently expressed in Escherichia coli under the control of the tac promoter. The recombinant T. thermophilus Glu-tRNA synthetase was extremely thermostable and was purified to homogeneity by heat treatment and three-step column chromatography. Single crystals of T. thermophilus Glu-tRNA synthetase were obtained from poly(ethylene glycol) 6000 solution by a vapor-diffusion technique. The crystals diffract X-rays beyond 0.35 nm. The crystal belongs to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters of a = 8.64 nm, b = 8.86 nm and c = 8.49 nm.     

An Activation of Synaptosomal Na+, K+-ATPase by a Novel Dibenzoxazepine Derivative (BY-1949) in the Rat Brain: Its Functional Role in the Neurotransmitter Uptake Systems

In search of factors mitigating the final outcome of ischemic and epileptic brain damage, we tested a novel dibenzoxazepine derivative (BY-1949), as the compound has been shown to be effective under these two conditions. First, using rat brain, we assessed whether or not BY-1949 affects the Na+,K(+)-ATPase activity. Although in vitro applications of either BY-1949 or its three major metabolites did not cause any apparent effects, both acute and chronic oral administrations of the compound (10 mg/kg) invariably increased the Na+,K(+)-ATPase activity in the synaptosomal plasma membranes by increasing Vmax values. Second, it was shown by this study that the drug treatment caused marked increases in the uptake of both glutamic acid and gamma-aminobutyric acid into the synaptosomes. These results suggest that the activity against ischemic/epileptic brain damage by BY-1949 is explicable, at least partly, in terms of improvement of ionic derangements across the neural membranes via Na+,K(+)-ATPase activation.     

Protective mechanism of sodium molybdate against the acute toxicity of cadmium in rats. II. Prevention of cytoplasmic acidification

In order to clarify the protective mechanism of sodium molybdate against the acute toxicity of cadmium chloride in rat, the effect of in vivo sodium molybdate pretreatment on the cytotoxic action of cadmium in isolated hepatocytes was studied. The cytosolic pH of hepatocytes isolated from untreated rats immediately decreased with incubation in either neutral Hank's balanced salt solution (HBS), pH 7.4, containing 5 µM cadmium chloride minimum or acidic HBS (pH 7.1, 6.8, 6.5, and 6.2). The presence of 5 µM cadmium in HBS adjusted to pH 7.1 aggravated cytosalic acidification induced by the acidic medium alone. Cell viability of hepatocytes incubated in HBS at pH 6.2 was significantly reduced as compared to that of control cells in HBS at pH 7.4, but the presence of cadmium in the acidic HBS had no aggravating action against such a toxic action of the acidic medium although cellular uptake of the metal in the medium increased, as compared to that in HBS at pH 7.4. Molybdenum pretreatment alleviated cytoplasmic acidification induced by the treatment with HBS at pH 7.4 or 7.1 containing cadmium or by extracellular acid load wothout cadmium. This pretreatment also prevented the loss of cell viability induced by the treatment with HBS at pH 6.2 but could not attenuate that when cadmium was present in the medium.These facts suggest that molybdenum pretreatment alleviated the acute toxicity of cadmium in rat by preventing cytoplasmic acidification caused by the harmful metal.     

Enhanced growth of the red algaPorphyra yezoensis Ueda in high CO2 concentrations

Leafy thalli of the red algaPorphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO₂. It was found that the higher the CO₂ concentration, the faster the growth of the thalli. Aeration with elevated CO₂ lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO ₃ ^? to OH^? and CO₂ proceeded much faster than the dissociation of hydrated CO₂ releasing H⁺. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO₂ + HCO ₃ ^? + CO ₃ ^? ). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO₂ by marine algae is discussed.     

A possible new mechanism of temperature dependence of electron transfer in photosynthetic systems

A new theory for the electron transfer by the non-adiabatic process is formulated taking into account the origin shift and the frequency change of the vibration. The resultant formulas are quite similar to those of Jortner (Jortner, J. (1976) J. Chem. Phys. 64, 4860–4867) except that the free energy gap ΔG is used instead of the energy gap ΔE. By applying this theory to the photosynthetic electron transfer, the role of the remarkable temperature dependence of the electron transfer from cytochrome to P⁺ in Chromatium vinosum and the experimental data were reproduced very well using a small value of the coupling strength in contrast with the previous theory. This implies that proteins play a role to exclude many of the solvent molecules from the region of the electron transfer reaction between the donor and acceptor molecules. The negative activation process in the back electron transfer from Q^?_A to P⁺, the very slow back electron transfer from I^? to P⁺ and the solvent isotope effect on the cytochrome oxidation are also successfully explained by this new theory. It is shown that even a qualitative conclusion as to the molecular parameters obtained from the temperature dependence of the electron transfer is different between the present theory and that of Jortner.     

The Amino Acid Sequence of the Tryptophan-Containing Subunit (α-Subunit) of Bovine Brain S-100 Protein

Abstract: The tryptophan-containing subunit (α-subunit) of bovine brain S-100 protein was purified from a S -aminoethyl derivative of S-100a protein, and its amino acid sequence was determined. The α-subunit contained 93 residues, including one tryptophan, and had a molecular weight of 10,400. The sequence shows an extensive homology (58% identity) to the sequence of another "tryptophan-free" subunit (β-subunit) found in both S-100a and S-100b protein, and has a calcium binding site characteristic of the "E-F hand" proteins, such as calmodulin or troponin C. The tryptophan residue is located at position 90 which is presumably adjacent to the C-terminal end of the α-helix following the calcium binding loop, and thus appears likely to serve as a specific probe in structure-function studies of S-100a protein.     

Angeloylcumambrin-B,an antimicrobial sesquiterpene lactone from Chrysanthemum ornatum var. Spontaneum

Angeloylcumambrin-B, a new antimicrobial guaianolide sesquiterpene lactone, was isolated from Chrysanthemum ornatum and the structure was determined by a combination of chemical and physical methods.