Methyltransferase involved in ribosomal biogenesis. Specifically catalyzes the N1-methylation of the pseudouridine corresponding to position 914 in M.jannaschii 16S rRNA (By similarity). a pseudouridine in 16S/18S rRNA + S-adenosyl-L-methionine = an N(1)-methylpseudouridine in 16S/18S rRNA + H(+) + S-adenosyl-L-homocysteine Homodimer. Belongs to the class IV-like SAM-binding methyltransferase superfamily. RNA methyltransferase NEP1 family.