Activity Of Transfer RNA Methyltransferases During Insect Metamorphosis

Abstract

Transfer RNA (tRNA) methyltransferases were partially purified from Manduca sexta prepupa larvae and 2-day-old pupae. The purification procedure involved pH 5 precipitation, gel filtration to remove endogenous inhibitors and activators, and ammonium sulfate precipitation. To ensure maximal activation of all preparations, 0.36 M ammonium acetate was used in the reaction mixture. Escherichia coli B tRNA was the methyl accepting substrate, and ¹⁴CH₃-S-adenosylmethionine was the methyl donor. The prepupa larvae had a specific activity of 140 units/mg protein. The 2-day-old pupae had a specific activity of 430 units/mg protein.