O-Ribosyl-phosphate purine as a constant modified nucleotide located at position 64 in cytoplasmic initiator tRNAsMetof yeasts

The unknown modified nucleotide G*, isolated from both Schizosaccharomyces pombe and Torulopsis utilis initiator tRNAs(Met), has been identified as an O-ribosyl-(1"----2')-guanosine-5"-phosphate, called Gr(p), by means of HPLC, UV-absorption, mass spectrometry and periodate oxidation procedures. By comparison with the previously published structure of Ar(p) isolated from Saccharomyces cerevisiae initiator tRNA(Met), the (1"----2')-glycosidic bond in Gr(p) has been postulated to have a beta-spatial conformation. The modified nucleotide Gr(p) is located at position 64 in the tRNA(Met) molecules, i.e. at the same position as Ar(p). Since we have also characterized Gr(p) in Candida albicans ini…

The primary structure of cytoplasmic initiator tRNAMetfromSchizosaccharomyces pombe

Presence and coding properties of 2'-O-methyl-5-carbamoylmethyluridine (ncm5Um) in the wobble position of the anticodon of tRNA(Leu) (U*AA) from brewer's yeast.

AbstractThe unknown modified nucleoside U* has been isolated by enzymatic and HPLC protocols from tRNALeu(U*AA) recently discovered in brewer's yeast. The pure U* nucleoside has been characterized by electron impact mass spectroscopy, and comparison of its chromatographic and UV-absorption properties with those of appropriate synthetic compounds. The structure of U* was established as 2′-O-methyl-5-carbamoylmethyluridine (ncm5Um). The yeast tRNALeu (U*AA) is the only tRNA so far sequenced which has been shown to contain ncm5Um. The location of such a modified uridine at the first position of the anticodon restricts the decoding property to A of the leucine UUA codon.

2'-O-methyl-5-formylcytidine (f5Cm), a new modified nucleotide at the 'wobble' of two cytoplasmic tRNAs Leu (NAA) from bovine liver.

The nucleotide analysis of a cytoplasmic tRNA(Leu) isolated from bovine liver revealed the presence of an unknown modified nucleotide N. The corresponding N nucleoside was isolated by different enzymatic and chromatographic protocols from a partially purified preparation of this tRNA(Leu). Its chemical characterization was determined from its chromatographic properties, UV-absorption spectroscopy and mass spectrometric measurements, as well as from those of the borohydride reduced N nucleoside and its etheno-trimethylsilyl derivative. The structure of N was established as 2'-O-methyl-5-formylcytidine (f5CM), and its reduced derivative as 2'-O-methyl-5-hydroxy-methylcytidine (om5Cm). By sequ…

Identification and structural characterization of O-beta-ribosyl-(1"----2')-adenosine-5"-phosphate in yeast methionine initiator tRNA.

We report in this paper on the complete structure determination of the modified nucleotide A*, now called Ar(p), that was previously identified in yeast methionine initiator tRNA as an isomeric form of O-ribosyl-adenosine bearing an additional phosphoryl-monoester group on its ribose2 moiety. By using the chemical procedure of periodate oxidation and subsequent beta-elimination with cyclohexylamine on mono- and dinucleotides containing Ar(p), we characterized the location of the phosphate group on the C-5" of the ribose2 moiety, and the linkage between the two riboses as a (1"----2')-glycosidic bond. Since the structural difference between phosphatase treated Ar(p) and authentic O-alpha-rib…