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. Author manuscript; available in PMC: 2011 Jan 21.
Published in final edited form as: FEBS Lett. 2010 Jan 21;584(2):278–286. doi: 10.1016/j.febslet.2009.11.075

Figure 2.

Figure 2

Proposed mechanism for T. thermophilus TrmFO-catalyzed formation of ribothymidine at position 54 of tRNA. Nucleophilic attack on C6 generates in turn a nucleophilic C5 position that attacks the methylene group of 5,10-methylenetetrahydrofolate (MTHF). The covalent intermediate (upper right) is resolved by base abstraction of a proton at C5, analogous to the TrmA mechanism depicted in Figure 1A, but producing a methylene group at C5. The methylene is reduced to a methyl group by a redox chain involving both FAD and NADP+ cofactors.