23S rRNA (uracil<sup>747</sup>-C<sup>5</sup>)-methyltransferase (, YbjF, RumB, RNA uridine methyltransferase B) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (uracil<sup>747</sup>-C<sup>5</sup>)-methyltransferase. This enzyme catalyses the following chemical reaction
The enzyme specifically methylates uracil<sup>747</sup> at C<sup>5</sup> in 23S rRNA.