Aminoacylation of tRNA. Magnesium requirement and spermidine effect.

The aminoacylation of tRNA has been fommlated as a two step reaction [ 11. The first reaction is the activation of the amino acid, and the second is the transfer of the activated amino acid onto the tRNA. Takeda and co-workers have proposed that only the first reaction requires magnesium ions; whereas, the magnesium ions are not necessary for the overall reaction [2,3]. This concept has caused confusion and necessitated a revision of the theory of the two step reaction [5]. We have reinvestigated the effects of spermidine and magnesium ions on the aminoacylation of several tRNAs according to the procedures previously reported [ 2-41. The experiments described herein lead to conclusions essentially different from those of Takeda and Igarashi [2]. Magnesium ions are essential in the aminoacylation of most, if not all tRNAs and cannot be substituted by spermidine.