ENZYMATIC MECHANISM OF TRANSFER-RNA (M(5)U54)METHYLTRANSFERASE

tRNA (m(5)U54)methyltransferase (RUMT) catalyzes the methylation of ur idine 54 of transfer RNA by S-adenosyl-L-methionine. In this report, w e present the enzymatic mechanism of RUMT, including the stereochemica l course of the methylation reaction, and discuss RUMT-tRNA recognitio n. As part of its enzymatic mechanism, we postulate that RUMT catalyze s the disruption of RNA-RNA contacts. We also show that many nucleotid e substitutions can be made in the T-loop of tRNA without affecting RU MT binding, indicating that the recognition of the T-loop by RUMT is n ot stringent.