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S Uesugi

Publications and source records attributed to S Uesugi.

At least 127 records · Page 7Linked to original sources
PubMed1989

Synthesis and properties of RNA with catalytic activity.

Ribooligonucleotides, which form the self-cleavage domain of a satellite RNA of tobacco ringspot virus, were synthesized by the solid-phase phosphoramidite method using o-nitrobenzyl groups for 2'-hydroxyl protection. The oligomers were obtained in quantities sufficient for NMR measurement. Specific cleavage at an expected site was observed when the three RNA fragments were mixed in the presence of magnesium ions.

Base Sequence↗
PubMed1989

NMR studies on DNA hairpin structures with a five nucleotide loop.

One- and two-dimensional NMR experiments have been undertaken to investigate the structure of DNA hairpins with a five nucleotide loop. Analysis of proton NMR spectra suggests that the four hairpin structures examined have some common structural features; B-type conformation in the stem region and the same stacking pattern, 5' (XXX-turn-XX) 3', in the loop region. The phosphorus NMR spectra suggest that the conformational changes in the loop region affect the backbone conformation of the stem duplex.

Base Sequence↗
PubMed1989

The molecular structure of Okazaki fragment r(CGCA)d(AAAAAGCG):d(CGCTTTTTTGCG) in solution.

The hetero duplex molecule, r(CGCA)d(AAAAAGCG):d(CGCTTTTTTGCG) which corresponds to Okazaki fragment was synthesized and its molecular structure has been analyzed by NMR study. The RNA strand of RNA-DNA hybrid region adopts A-form and DNA strand of the same region deviates from the standard B-form. The conformation of DNA-DNA duplex segment belongs to B-form. The hybrid-DNA duplex junction shows a structural discontinuities, A-B junction. The same conformational characteristic of oligo(dA): oligo(dT) tract as that of DNA oligomer which has same base sequence has been observed.

Base Sequence↗
PubMed1988

A possible recognition mode of mRNA cap terminal structure by peptide: cooperative stacking and hydrogen-bond pairing interactions between m7GpppA and Trp-Leu-Glu.

1H-NMR and fluorescence spectroscopic studies on the interaction between the Trp-Leu-Glu and m7GpppA have shown a specific binding mode, in which the pi-pi stacking interaction of the Trp indole ring and the hydrogen-bond pairing of Glu carboxyl side group with 7-methylguanine base are simultaneously formed.

Base Composition↗
PubMed1988

Increase in nucleolytic activity of ribonuclease T1 by substitution of tryptophan 45 for tyrosine 45.

The preparation and analysis of a mutant ribonuclease (RNase) T1 which possesses higher nucleolytic activity than the wild-type enzyme are described. The gene for the mutant RNase T1 (Tyr45----Trp45), in which a single amino acid at the binding site of the guanine base has been changed, was constructed by the cassette mutangenesis method using a chemically synthesized gene [Ikehara, M. et al. (1986) Proc. Natl Acad. Sci. USA 83, 4695-4699]. In order to reduce the nucleolytic activity of the enzyme in vivo, this gene was expressed in Escherichia coli as a fused protein connected through methionine residues to other proteins at both the N- and C-termini. After liberation from the fused protein by cleavage with cyanogen bromide at the methionine junctions, the mutant RNase T1 was purified by column chromatography. The nucleolytic activity toward pGpC increased to 120% of that of wild-type RNase T1. The kinetic parameters of the mutant enzyme demonstrate that this higher nucleolytic activity is due to a higher affinity for the substrate, probably because of an increased stacking effect in the binding pocket for the guanine base. This mutant enzyme also possessed a higher nucleolytic activity against pApC than wild-type RNase T1.

Base Sequence↗
PubMed1988

Atrial natriuretic polypeptide depresses angiotensin II induced excitation of neurons in the rat subfornical organ in vitro.

The effects of atrial natriuretic polypeptide (ANP) on the extracellularly recorded activity of neurons in the subfornical organ (SFO) were investigated in rat brain slice preparations by adding the peptide to the perfusion medium. Eight (14%) of 56 SFO neurons were inhibited and none of the cells were excited by ANP at 10(-7) M. Of 42 SFO neurons tested with both ANP and angiotensin II (AII) at 10(-7) M, 4 (10%) cells were inhibited by ANP and excited by AII, the remainder responded to either one or other of the peptides but not both or were unresponsive. In 13 (87%) of 15 SFO neurons, ANP at 10(-7) M depressed by more than 40% the excitation induced by AII at 10(-7) M, while ANP did not always depress the excitation induced by raising the extracellular potassium concentrations in 6 SFO cells tested. We conclude that ANP strongly depresses AII-induced excitation in all SFO neurons, although it has very weak inhibitory effects on spontaneous activity, thus ANP may act as a neuromodulator in the SFO.

Angiotensin II↗
PubMed1988

Hybrid hexanucleotide duplex containing cyclonucleotides and deoxynucleotides: the d(TA) segment can adopt a high anti left-handed double-helical structure.

It is known that oligonucleotides containing cyclonucleosides with a high anti (intermediate between anti and syn) glycosidic conformation adopt left-handed, single- and double-helical structures [Uesugi, S., Yano, J., Yano, E., & Ikehara, M. (1977) J. Am. Chem. Soc. 99, 2313-2323]. In order to see whether DNA can adopt the high anti left-handed double-helical structure or not, a self-complementary hexanucleotide containing 6,2'-O-cyclocytidine (C(o)), 8,2'-O-cycloguanosine (G(o)), thymidine, and deoxyadenosine, C(o)G(o)dTdAC(o)G(o), was synthesized. Imino proton NMR spectra and the results of nuclear Overhauser effect experiments strongly suggest that C(o)G(o)dTdAC(o)G(o) adopts a left-handed double-helical structure where the deoxynucleoside residues are involved in hydrogen bonding and take a high anti glycosidic conformation. A conformational model of the left-handed duplex was obtained by calculation with energy minimization. Thus it appears that DNA can form a high anti, left-handed double helix under some constrained conditions, which is quite different from that of Z-DNA.

DNA↗
PubMed1988

Glu 46 of ribonuclease T1 is an essential residue for the recognition of guanine base.

The Glu 46 of ribonuclease T1, which is assumed to interact with Nl of the guanine residue in RNA by a hydrogen bond from the result of X-ray analysis, was changed to alanine by site-directed mutagenesis and its function examined. The nucleolytic activity of the Ala 46 mutant enzyme against pGpC decreased to 0.4% of that of the wild-type enzyme, on the other hand its activity against pApC increased. This result suggests that the Glu 46 is essential for the recognition of the guanine base but that it also interferes with the recognition of the adenine base.

Alanine↗
PubMed1988

Conformational properties of the guanine-binding site of ribonuclease T1 inferred from the X-ray structure and protein engineering.

Recognition by ribonuclease T1 of guanine bases via multidentate hydrogen bonding and stacking interactions appears to be mediated mainly by a short peptide segment formed by one stretch of a heptapeptide, Tyr42-Asn43-Asn44-Tyr45-Glu46-Gly47- Phe48. The segment displays a unique folding of the polypeptide chain--consisting of a reverse turn, Asn44-Tyr45-Glu46-Gly47, stabilized by a hydrogen-bond network involving the side chain of Asn44, the main-chain atoms of Asn44, Gly47 and Phe48 and one water molecule. The segment is connected to the C terminus of a beta-strand and expands into a loop region between Asn43 and Ser54. Low values for the crystallographic thermal parameters of the segment indicate that the structure has a rigidity comparable to that of a beta-pleated sheet. Replacement of Asn44 with alanine leads to a far lower enzymatic activity and demonstrates that the side chain of Asn44 plays a key role in polypeptide folding in addition to a role in maintaining the segment structure. Substitution of Asn43 by alanine to remove a weak hydrogen bond to the guanine base destabilized the transition state of the complex by 6.3 kJ/mol at 37 degrees C. In contrast, mutation of Glu46 to alanine to remove a strong hydrogen bond to the guanine base caused a destabilization of the complex by 14.0 kJ/mol. A double-mutant enzyme with substitutions of Asn43 by a histidine and Asn44 by an aspartic acid, to reproduce the natural substitutions found in ribonuclease Ms, showed an activity and base specificity similar to that of the wild-type ribonuclease Ms. The segment therefore appears to be well conserved in several fungal ribonucleases.

Amino Acid Sequence↗
PubMed1988

Synthesis and application of a new phosphorylating agent: S-(N-monomethoxytritylaminoethyl)-O-(o-chlorophenyl)phosphorothi oate.

A new phosphorylating agent, S-(N-monomethoxytritylaminoethyl)-O-(O-chlorophenyl) phosphorothioate, was prepared and reacted with a 5'-hydroxyl group of an oligonucleotide using 1-mesitylene-sulfonyl-3-nitrotriazole (MSNT) as a condensing agent. After base labile protecting groups were removed, the partially deprotected oligonucleotide was separated on a reversed phase column and converted to the oligonucleotide with an aminoethyl or a phosphoryl group at the 5'-end by treatment with 80% acetic acid or iodine-water, respectively. The syntheses of ppT, pppT, A5'pp5'T and A5'ppp5'T were also performed by treatment of 5'-O-(N-monomethoxytritylaminoethylthiophosphoryl) thymidine with tri-n-octylammonium salt of phosphoric acid, pyrophosphoric acid, pA and ppA, respectively.

Indicators and Reagents↗