Catalysis of the transfer of a methyl group from S-adenosyl-L-methionine to the delta-nitrogen atom of peptidyl-arginine residues. The reaction is S-adenosyl-L-methionine + [protein]-L-arginine = S-adenosyl-L-homocysteine + [protein]-N5-methyl-L-arginine.
protein arginine N5-methylase activity
;
protein-arginine delta-N-methyltransferase activity
;
type IV PRMT activity
;
type IV protein arginine methyltransferase activity