Cytokinin Activity: Localization in Transfer RNA Preparations

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Science  09 Dec 1966:
Vol. 154, Issue 3754, pp. 1354-1356
DOI: 10.1126/science.154.3754.1354


Transfer RNA from yeast, liver, and Escherichia coli has cytokinin activity in the tobacco callus bioassay, whereas ribosomal RNA from yeast is inactive. In contrast to fractions of yeast transfer RNA rich in serine acceptor and cytokinin activity, preparations (70 to 90 percent pure) of arginine transfer RNA2, glycine transfer RNA, phenylalanine transfer RNA, and valine transfer RNA1 and of highly purified alanine transfer RNA from yeast were inactive at concentrations of 20 to 2500 micrograms per liter. One molecule of 6-(γ,γ-dimethylallylamino) purine per 20 molecules of yeast tRNA would account for the observed cytokinin activity. The number of major molecular species contributing to cytokinin activity of transfer RNA, therefore, must be small.