Enzymatic mechanism of tRNA (m5U54)methyltransferase.

tRNA (m5U54)methyltransferase (RUMT) catalyzes the methylation of uridine 54 of transfer RNA by S-adenosyl-L-methionine. In this report, we present the enzymatic mechanism of RUMT, including the stereochemical course of the methylation reaction, and discuss RUMT-tRNA recognition. As part of its enzymatic mechanism, we postulate that RUMT catalyzes the disruption of RNA-RNA contacts. We also show that many nucleotide substitutions can be made in the T-loop of tRNA without affecting RUMT binding, indicating that the recognition of the T-loop by RUMT is not stringent.