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Biomedical subjects

Y Iitaka

Publications and source records attributed to Y Iitaka.

At least 91 records · Page 5Linked to original sources
PubMed1978

Crystal structure of monoclinic ribonuclease-S at 4 A resolution. The mode of binding of 4-thiouridylic acid and a fragment of folic acid, p-aminobenzoylglutamic acid.

A four-A electron density map was calculated for the monoclinic crystal of ribonuclease-S (RNase-S) based on two heavy-atom derivatives. Close geometrical similarity was found between the two crystallographically independent RNase-S molecules (called molecules ZA and ZB) in this crystal and that (called molecule Y) in the trigonal crystal. Using the rotational and translational parameters relating these three molecules, it was established that the crystallographic two-fold symmetry between the two molecules ZA in the monoclinic crystal was exactly identical to that between the two molecules Y in the trigonal crystal, suggesting the tendency of RNase-S molecules to associate in this way although the interaction is weak. The 4-A difference Fourier maps calculated for the monoclinic crystal established the following conclusions. (1) 4-Thiouridine-2'(3')-monophosphates binds to the B1 and R1 sites like other pyrimidine nucleoside-2'(3')-monophosphates as expected from previous spectrophotometric studies, but not to the B2 site even at the concentration of 20 mM. An attempt to visualize the photoproduct generated by irradiation of near-ultraviolet light in this complex failed. (2) p-Aminobenzoylglutamic acid, a fragment of folic acid, seems to bind to RNase-S with its benzene ring close to the B2 site and the alpha-carboxylate group close to the p1 site. The model is compatible with most of the chemical results obtained by Sawada et al. ((1977) Biochim. Biophys. Acta 479, 188-197).

4-Aminobenzoic Acid↗
PubMed1978

Crystallization of arginine-, formylmethionine-tyrosine-, and glycine-transfer RNAs from Escherichia coli.

Crystals as large as 0.5 X 0.3 X 0.2 mm of purified arginine-transfer RNA from Escherichia coli have been prepared by a vapour diffusion method. X-ray diffraction photographs showed that the crystals gave reflections up to 3.7 A spacing. They have a trigonal space group P31 2 1 (OR P32 2 1) and cell-dimensions a=97.2, b=97.2, c=94.8A. Crystals of a mercury derivative of this transfer RNA have also been obtained, and an X-ray diffusion photography of one of them is presented. Formylmethionine-transfer RNA from E. coli was crystallized in various forms, and the appearance of the polymorphs was found to depend upon the amount of spermine in the solution from which the crystallization took place. Crystals of tyrosine-transfer RNA and glycine-transfer RNA have also been obtained.

Arginine↗
PubMed1978

Crystal structure of a protein proteinase inhibitor, SSI (Streptomyces subtilisin inhibitor), at 4 A resolution.

The crystal structure of a protein proteinase inhibitor, SSI (Streptomyces subtilisin inhibitor), which strongly inhibits bacterial alkaline proteinases specifically, was determined at 4 A resolution using four heavy-atom derivatives. The SSI molecule can be described as an ellipsoid of about 30 X 40 X 65 A composed of two identical subunits each having dimensions of about 35 X 25 X 40 A and a molecular weight of 11,483. The subunit has an extensive beta-sheet structure, but no long alpha-helices are present. Based on the binding sites of platinum reagents known to form coordination complexes with methionine, it is speculated that the P1 residue, Met 73, of the reactive site is at the protruding edge of the subunit. At the subunit-subunit interface, a beta-sheet of one subunit is stacked on top of the corresponding beta-sheet of the other subunit.

Bacterial Proteins↗
PubMed1977

Crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor, at 2.3 angstrom resolution.

The crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor which strongly inhibits bacterial alkaline proteinases, was determined at 2.3 angstrom resolution. The subunit (molecular weight, 11,485) of this dimeric molecule has a unique fold of polypeptide chain with a five-fold anti-parallel beta-sheet structure (about 21% of the 113 amino acid residues) and two small segments of alpha-helices (about 16%). The region around the apparent reactive site, Met(73)-Val(74), is held tight by a combination of various structural features. The conformation of this region seems to have close similarity to that found in substrate analogues of low molecular weight bound to subtilisin BPN'.

Crystallography↗
PubMed1977

Structure of aplasmomycin.

A new antibiotic, aplasmomycin, was isolated from a broth cultivated with a marine isolate of actinomycete, and inhibits Gram-positive bacteria in vitro and Plasmodium berghei in vivo. It is a natural ionophore and the structure of the Ag-salt was solved by an X-ray crystallographic analysis. It has symmetric structure having boron in the centre of the molecule.

Anti-Bacterial Agents↗