Tyunosin Ukita

Chemical Methylation of Inorganic Mercury with Methylcobalaiin, a Vitamin B12 Analog

Chemical methylation of mercuric chloride with methylcobalamin has been studied. Methylated mercury was detected by gas chromatography; and analysis of the products of the reaction by thin-layer chromatography revealed that the methylation proceeded at a remarkably high rate when methylcobalamin and inorganic mercury were mixed. Dimethylmercury was an initial product of the reaction.

Purification of galactose-binding phytoagglutinins and phytotoxin by affinity column chromatography using sepharose

Phytoagglutinine, welche Galaktose spezifisch binden, wurden mit Chromatographie an Sepharose gereinigt. Zwei Fraktionen ausRicinus communis-Agglitomom wiurden durch Gelfiltration mittels Bio-gel getrennt: die früh eluierte Fraktion zeigte starke Agglutinationsaktivität und schwache Toxizität, während die später eluierte Fraktion eine schwache Agglutinatinsaktivität bei starker Toxizität zeigt.

The selective degradation of pyrimidines in nucleic acids by permanganate oxidation.

Abstract In our current studies on the chemical modifications of nucleic acids, we have reported on the selective reaction of semicarbazide derivatives with cytidine residues ( Hayatsu and Ukita, 1964 , Hayatsu and Ukita, 1966 ; Hayatsu et al. , 1966 ; Kikugawa et al., 1967a , Kikugawa et al., 1967b ). In this paper we describe a procedure by which pyrimidines in the single stranded region of nucleic acids are degraded selectively. Furthermore, reaction conditions are presented whereby thymidylic acid is exclusively attacked while other deoxyribonucleotides are virtually intact. This procedure consists of the permanganate oxidation of the nucleic acid under relatively mild reaction conditions of pH 6.7 and 0°C.

Specificity of yeast glutamic acid transfer RNA for codon recognition

Two species of tRNA for glutamic acid (glutamic acid tRNAs I and III) were separated from yeast tRNA, and the stimulation of their binding to Escherichia coli ribosomes by the trinucleotides GpApA and GpApG, which are known to be codons for glutamic acid, was tested. The specificity of these two species of glutamic acid tRNAs for codon recognition was further studied by testing the transfer of glutamic acids to the specific amino acid position in rabbit hemoglobin by these tRNA species. The results of these studies showed that yeast glutamic acid tRNAs I and III specifically recognized the glutamic acid codons GpApG and GpApA, respectively. The codons for glutamic acid on the hemoglobin mRNA were tentatively assigned. It is the first clear demonstration that a codon containing adenosine residue in the third letter was specifically recognized by a tRNA.

Structural studies on a yeast glutamic acid tRNA specific to GAA codon.

Abstract 1. 1. Yeast tRNA Glu 3 , which recognizes GAA but not GAG as codon for glutamic acid, was purified by column chromatography to approx. 85 % purity. 2. 2. The fragments produced by complete digestion of tRNA Glu 3 with ribonuclease T 1 were characterized by the combination of various enzymatic degradations. This tRNA was found to have GpCpC as 3′-terminal sequence, pUpCpCpGp as 5′-terminal sequence and TpψpCpGp as a common sequence.0 3. 3. The tRNA Glu 3 contains 7 minor nucleosides, i.e. 3 pseudouridines, one ribothymidine, one 5-methylcytidine, one dihydrouridine and a 2-thiouridine derivative ( S ). This tRNA does not contain O-methylated and N-methylated nucleosides. 4. 4. The 2-thiouridine derivative ( S ) was identified as 2-thiouridine-5-acetic acid methyl ester, which was first found in an aminoacid-specific tRNA hitherto purified. The sequence of a ribonuclease T 1 -digest oligonucleotide which contained S was determined as CpUp S pUpCpApCpCpGp, and its partial sequence S pUpCp was proposed to be the anticodon of this tRNA. The specific GAA codon recognition by this tRNA Glu 3 was reasonably explained by the fact that S can pair with A but hardly pairs with G.

Distribution of inorganic, aryl, and alkyl mercury compounds in rats

Abstract Mercuric chloride (MC), phenylmercuric chloride (PMC), ethylmercuric chloride (EMC), S-ethylmercuric cysteine (EMCys), and n -butylmercuric chloride (BMC) labeled with 203 Hg were subcutaneously administered to rats, and the distribution and excretion of mercury were determined. In general, alkylmercury compounds (EMC, EMCys, and BMC) were excreted more slowly and were retained in higher concentration for a longer time in the body than MC and PMC. Several alkylmercury compounds revealed different metabolic behavior which depended on the carbon-chain length of the alkyl group. Distribution of mercury in the brain was found to depend on the structure of the mercury compounds. The relation between the neurotoxicity and the structure of the mercury compounds was discussed.

Chemical modification of tRNAyeastTyr with bisulfite. A new method to modify isopentenyladenosine residue

Abstract When tRNAyeastTyr was treated with bisulfite at pH 7, the uracil (U) residue next to the 5′-end of the anticodon and the isopentenyladenine (iA) residue adjacent to the 3′-end of it were chemically modified. On treatment of this transformed tRNA with weak alkali, the modified U residue regenerated U, while the modified iA remained unaltered. The modification of both the U and iA residues did not affect the amino acid accepting activity of the tyrosine tRNA, while the specific modification of the iA residue resulted in the decrease of the ability of the tyrosyl tRNA to bind to the messenger-ribosome complex.

Anticodon structure of GAA-specific glutamic acid tRNA from yeast

Abstract A yeast glutamic acid tRNA, which specifically recognizes GAA codon but not GAG codon, was digested with RNase T1 and the nucleotide sequences of the fragments were determined. A minor nucleoside, 2-thiouridine derivative ( S ), was found in the presumed anticodon, S pUpCp. The possible function of this minor nucleoside for the specific recognition of GAA by this tRNA was discussed.

The modification of nucleosides and nucleotides

Abstract 1. Semicarbazide has been found to replace the C-4 amino group of cytidine and deoxycytidine with a semicarbazido residue. The reaction occurred at a maximum rate at pH 4.2 and followed pseudo-first-order kinetics. 2. The reaction was found to be absolutely specific for cytosine nucleosides or nucleotides and no reaction between semicarbazide and adenosine, guanosine, uridine, or their corresponding nucleotides was observed in the pH range 4.0–9.5 and 37°. 3. The product of the reaction between semicarbazide and cytidine was identified as 4-deamino-4-semicarbazido cytidine. This latter compound was synthesized from 2′,3′,5′-tri- O -benzoyl-4-thiouridine by reaction with semicarbazide followed by debenzoylation. 4. 4-Deamino-4-semicarbazido cytidine 2′,3′-cyclic phosphate was more slowly hydrolyzed than uridine 2′,3′-cyclic phosphate by bovine pancreatic ribonuclease (ribonucleate pyrimidine-nucleotido-2′-transferase (cyclizing), EC 2.7.7.16). 5. An application of the reaction to the selective modification of cytidine or deoxycytidine residues in RNA and DNA is proposed.

Mercury compounds in the blood of rats treated with ethylmercuric chloride

Ethylmercuric chloride (EMC) labeled with 203Hg was administered to rats, and the chemical nature of the mercury compound which accumulated in the blood was investigated. More than 97% of the total mercury in the blood of the EMC-treated rats was extracted with dithizone as organic mercury dithizonate and the organic mercury compounds liberated as the chloride from blood was identified by comparison with authentic ethylmercuric chloride. The ethylmercury residue in the blood was found to be bound to hemoglobin, and it was detected as S-ethylmercuric cysteine in the pronase digest of the bound hemoglobin. Form these results, it was concluded that the ethylmercury residue should accumulate in the blood, binding with SH groups of cysteine residues by a mercaptide linkage to the hemoglobin molecule. In vitro experiments of the distribution of EMC in the blood showed that EMC had a high affinity for the inside of the membrane of erythrocytes as was previously seen in vivo, and that mercury compound, once combined with hemoglobin, was transferred with difficulty through the stroma.