the methyltransferase which forms n2-methylguanine in the region between the dihydrouridine loop and the acceptor stem ( 2mg i ) , when assayed using purified trna as substrate , shows high activity with 3 -- 5 mm sperimidine or 20 mm putrescine and significantly lower rates of methylation with 200 -- 350 mm ammonium acetate or 1 -- 10 mm magnesium acetate .
C0025831
methyltransferase
C0025723
methylation