(1) S-adenosyl-L-methionine + cytidine34 in tRNA = S-adenosyl-L-homocysteine + 2'-O-methylcytidine34 in tRNA;
(2) S-adenosyl-L-methionine + 5-carboxymethylaminomethyluridine34 in tRNALeu = S-adenosyl-L-homocysteine + 5-carboxymethylaminomethyl-2'-O-methyluridine34 in tRNALeu
cytidine34 in tRNA;
5-carboxymethylaminomethyluridine34 in tRNALeu
2'-O-methylcytidine34 in tRNA;
5-carboxymethylaminomethyl-2'-O-methyluridine34 in tRNALeu
The enzyme from Escherichia coli catalyses the 2'-O-methylation of cytidine or 5-carboxymethylaminomethyluridine at the wobble position at nucleotide 34 in tRNALeuCmAA and tRNALeucmnm5UmAA. The enzyme is selective for the two tRNALeu isoacceptors and only methylates these when they present the correct anticodon loop sequence and modification pattern. Specifically, YibK requires a pyrimidine nucleoside at position 34, it has a clear preference for an adenosine at position 35, and it fails to methylate without prior addition of the N6-(isopentenyl)-2-methylthioadenosine modification at position 37.