S-adenosyl-L-methionine-dependent protein-arginine N-methyltransferase that methylates the delta-nitrogen atom of arginine residues to form N5-methylarginine (type IV) in target proteins (PubMed:9873020). Monomethylates ribosomal protein L12 (RPL12A/RPL12B) at 'Arg-67' (PubMed:11856739). Monomer. Interacts with nucleoporins NUP49, NUP57 and NUP100. Appears often very close to the nuclear membrane and the nuclear pores. Measured from a recombinant protein expressed in E.coli. Present with 1600 molecules/cell in log phase SD medium. Belongs to the class I-like SAM-binding methyltransferase superfamily. RMT2 methyltransferase family.