[tRNA-methylase study of the extreme thermophile, Thermus flavus]

tRNA methylases were studied in the extreme thermophilic culture of Thermus flavus, strain 71. Like E. coli, the culture contained only those tRNA methylases which catalysed the formation of m1A and m7G. Mg2+, Ca2+ and Na+ ions activated tRNA methylases of Thermus flavus in the series Mg greater than Ca greater than Na while Mn2+ ions inhibited the enzyme. The activity of tRNA methylases was higher in T. flavus than in E. coli, and required less protein and time for exhaustive methylation of tRNA preparations. The overall activity of methylases in T. flavus at 70 degrees C was 5-6 times higher than at 40 degrees C; the elevation of temperature had different effect on various methylases: the activity of m1A methylase increased 13-fold whereas that of m7G methylase only twofold.