23S rRNA (guanine748-N1)-methyltransferase (EC 2.1.1.188, Rlma(II), Rlma2, 23S rRNA m1G748 methyltransferase, RlmaII, Rlma II, tylosin-resistance methyltransferase RlmA(II), TlrB, rRNA large subunit methyltransferase II) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (guanine748-N1)-methyltransferase. This enzyme catalyses the following chemical reaction S-adenosyl-L-methionine + guanine748 in 23S rRNA S-adenosyl-L-homocysteine + 748 in 23S rRNA The enzyme specifically methylates guanine748 at N1 in 23S rRNA.