Putative protein methyltransferase using S-adenosyl-L-methionine as the methyl donor. May methylate a Gln residue in target proteins (By similarity). L-glutaminyl-[protein] + S-adenosyl-L-methionine = H(+) + N(5)-methyl-L-glutaminyl-[protein] + S-adenosyl-L-homocysteine Belongs to the eukaryotic/archaeal PrmC-related family.