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Biomedical subjects

Y Iitaka

Publications and source records attributed to Y Iitaka.

At least 73 records · Page 4Linked to original sources
PubMed1981

Preliminary crystal structure analysis of a microbial, guanine-specific ribonuclease St at 2.5 A resolution.

The three-dimensional structure of Ribonuclease St (RNase St), the extracellular ribonuclease from Streptomyces erythreus, has been deduced based on a preliminary electron density map at 2.5 A resolution. RNase St has a substrate specificity similar to ribonuclease T1 which catalyzes the splitting of the phosphodiester bond of guanylic acid. Crystals grown as diamond plates have space group C2 with unit cell parameters a=88.4, b=33.0, c=69.0 A, beta = 98.4 degrees having two enzyme molecules per asymmetric unit. Phases were obtained by use of KAu(CN)4, phenylmercuric acetate and UO2 (CH3COO)2. The overall dimensions of the molecule are 40 X 30 X 25 A. The most prominent secondary structural features are two turns of alpha-helix and a three strand stretch of antiparallel beta-sheet. The alpha-carbon backbone of RNase St seems to have no apparent correlation with that of ribonuclease A.

Models, Molecular↗
PubMed1981

Oxanosine, a novel nucleoside from actinomycetes.

Oxanosine, a novel nucleoside, has been isolated from the culture filtrate of a strain of Streptomyces. The structure was determined to be 5-amino-3-beta-D-ribofuranosyl-3H-imidazo [4,5-d] [1,3]oxazin-7-one by X-ray crystallographic analysis and chemical studies. Oxanosine showed weak antibacterial activity on peptone agar; for example, Escherichia coli K-12 (MIC 12.5 mcg/ml). The antibacterial activity was antagonized by addition of guanine, guanosine and 5'-guanylic acid. Oxanosine inhibited the growth of HeLa cells in vitro (IC50 32 mcg/ml) and suppressed the growth of L-1210 leukemia in mice. The primary action of oxanosine appears to be inhibition of GMP-synthetase. Intravenous injection of 4 mg of oxanosine to mice does not show any toxic sign.

Cell Division↗
PubMed1979

Three-dimensional structure of hyper-modified nucleoside Q located in the wobbling position of tRNA.

The hyper-modified nucleoside Q (queuosine) is exclusively located in the wobbling position of anticodons of tRNATyr tRNAHis, tRNAAsn and tRNAAsp that recognise codons NAUC (ref. 1). Queuosine and its hexose-containing derivatives are widely distributed in microorganisms, animals and plants. We confirm here the chemical structure of queuosine as 7-(3, 4-trans-4, 5-cis-dihydroxy-1-cyclopenten-3-ylaminomethyl)-7-deazaguanosine (Fig. 1). The unique structural features of Q are the unusual cyclopentenediol side chain and the 7-deazaguanine ring. Queuosine is one of the most complicated modified nucleosides found thus far.

Anticodon↗