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2′-O-methylation and inosine formation in the wobble position of anticodon-substituted tRNA-Phe in a homologous yeast in vitro system

par Droogmans, Louis ;Grosjean, Henri
Référence Biochimie, 73, 7-8, page (1021-1025)
Publication Publié, 1991

Article révisé par les pairs

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Résumé :

Four variants of yeast tRNA-Phe in which the anticodon and 3′-adjacent nucleotide (GmAAY) have been replaced by synthetic tetranucleotides NAAG (where N is each of the four canonical nucleosides G, C, U or A) are substrates for a yeast tRNA modification enzyme which catalyses the S-adenosyl-l-methionine dependent formations of Gm-34, Cm-34, Um-34, Am-34 and Im-34 (where Nm represents a 2′-O-methylnucleoside and I inosine). The kinetics of these nucleotides-34 2′-O-methylations reveal that yeast tRNA-Phe with G-34 (the natural substrate) is less efficiently modifiesbthan variants of the same tRNA containing U-34 and C-34. The formation of Am-34 in tRNA contaiing A-34 was found to be particularly inefficient. However, in this tRNA, we observed the formation of I-34 followed by a 2′-O-methylation (giving rise to Im-34). In the yeast in vitro system described here, inosine formation is not dependent on the addition of any cofactor including hypoxanthine; the mechanism of inosine formation in yeast tRNA might therefore be distinct from that found in higher eukaryotes. © 1991.