This enzyme, characterized from the yeast Saccharomyces cerevisiae, methylates the the Δ-nitrogen atom of arginine residues within proteins. Among its substrates are Arg67 of the ribosomal protein L12. cf. EC 2.1.1.319, type I protein arginine methyltransferase, EC 2.1.1.320, type II protein arginine methyltransferase, and EC 2.1.1.321, type III protein arginine methyltransferase.