Ichiro Hirao

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The three-dimensional structure of a short DNA fragment, d(GCGAAGC) exhibiting an extraordinarily stable hairpin structure was determined by nuclear magnetic resonance spectroscopy. Two possible models were obtained by molecular modelling using distance and torsion constraints. Only one of these two models is the correct structure, which can clearly explain(More)
RNA aptamers with affinity for the Ras-binding domain (RBD) of Raf-1 were isolated from a degenerate pool by in vitro selection. These aptamers efficiently inhibited the Ras interaction with the Raf-1 RBD, and also inhibited Ras-induced Raf-1 activation in a cell-free system. The RNA aptamer with the most potent inhibitory effect specifically inhibited the(More)
Pepocin, isolated from Cucurbita pepo, is a ribosome-inactivating protein (RIP). RIPs site-specifically recognize and depurinate an adenosine at position 4324 in rat 28 S rRNA, rendering the ribosome incapable of interacting with essential elongation factors. Aptamers that target pepocin were isolated from a degenerate RNA pool by in vitro selection. A(More)
Genetic alphabet expansion of DNA using unnatural base pair systems is expected to provide a wide variety of novel tools and methods. Recent rapid progress in this area has enabled the creation of several types of unnatural base pairs that function as a third base pair in polymerase reactions. Presently, a major topic is whether the genetic alphabet(More)
A small DNA fragment having a characteristic sequence d(GCGAAAGC) has been shown to form an extraordinarily stable mini-hairpin structure and to have an unusually rapid mobility in polyacrylamide gel electrophoresis, even when containing 7M urea. Here, we have studied the stability of the various sequence variants of d(GCGAAAGC) and the corresponding RNA(More)
RNA aptamers that bind to the Ras-binding domain (RBD) of a proto-oncogene product, Raf-1, were isolated from a pool of random sequences using a glutathione S-transferase-fused RBD (GST-RBD). The RNA molecules bind to the GST-RBD, but not to GST, with dissociation constants of about 300 nM. In contrast, these RNA aptamers do not bind to the Ras-binding(More)
Cytidine in the anticodon second position (position 35) and G or U in position 36 of tRNAArg are required for aminoacylation by arginyl-tRNA synthetase (ArgRS) from Escherichia coli. Nevertheless, an arginine-accepting amber suppressor tRNA with a CUA anticodon (FTOR1Delta26) exhibits suppression activity in vivo [McClain, W.H. & Foss, K. (1988) Science,(More)
A series of NH2-terminal truncated forms of human cysteine proteinase inhibitor, cystatin A, was prepared by genetic engineering using Escherichia coli harboring mutated genes. Each variant of cystatin A was efficiently expressed as a fused protein with porcine adenylate kinase and released by CNBr degradation after exchange of the sole inner Met to Leu.(More)
Short single-stranded DNA fragments carrying a GCGAAAGC sequence were found to move unexpectedly faster than other fragments of the same length in electrophoresis on a polyacrylamide gel containing a denaturing agent. The fragments were noted to have a stable structure even in 7M urea solution, but the stability cannot be explained simply on the basis of(More)
A suppressor tRNA(Tyr) and mutant tyrosyl-tRNA synthetase (TyrRS) pair was developed to incorporate 3-iodo-L-tyrosine into proteins in mammalian cells. First, the Escherichia coli suppressor tRNA(Tyr) gene was mutated, at three positions in the D arm, to generate the internal promoter for expression. However, this tRNA, together with the cognate TyrRS,(More)