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

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Abstract
The unknown modified nucleotide G*, isolated from both chizosaccharomyces pombe and Torulopsis utilis initiator tRNAsMet, has been identified as an Oribosy-(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 cerevlslae Initiator tRNAMet, the (1”—2')-glycosidic bond in Gr(p) has been postulated to have a α-spatial conformation. The modified nucleotide Gr(p) Is located at position 64 in the tRNAMet; molecules, i.e. at the same position as Ar(p). Since we have also characterized Gr(p) in Candida alblcans initiator tRNAMet, the phosphoribosylation of purine 64 can be considered as a constant nucleotide modification In the cytoplasmic initiator tRNAsMet of all yeast species so far sequenced. Precise evidence for the presence of Gr(p) in initiator tRNAsMet of several plants is also reported.