23S rRNA (uridine<sup>255</sup>2-2'-O)-methyltransferase (, Um(2552) 23S ribosomal RNA methyltransferase, heat shock protein RrmJ, RrmJ, FTSJ, Um<sup>2552</sup> methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (uridine<sup>2552</sup>-2'-O-)-methyltransferase. This enzyme catalyses the following chemical reaction
The enzyme catalyses the 2'-O-methylation of the universally conserved U<sup>2552</sup> in the A loop of 23S rRNA.