S-adenosyl-L-methionine-dependent and membrane-associated arginine methyltransferase that can both catalyze the formation of omega-N monomethylarginine (MMA) and asymmetrical dimethylarginine (aDMA) in proteins such as NIFK, myelin basic protein, histone H4, H2A and H2A/H2B dimer (PubMed:16051612, PubMed:17925405, PubMed:26876602, PubMed:26529540). Able to mono- and dimethylate EWS protein; however its precise role toward EWS remains unclear as it still interacts with fully methylated EWS (PubMed:18320585). L-arginyl-[protein] + S-adenosyl-L-methionine = H(+) + N(omega)-methyl-L-arginyl-[protein] + S-adenosyl-L-homocysteine L-arginyl-[protein] + 2 S-adenosyl-L-methionine = 2 H(+) + N(omega),N(omega)-dimethyl-L-arginyl-[protein] + 2 S-adenosyl-L-homocysteine Homodimer (PubMed:16051612, PubMed:26876602, PubMed:26529540). Tetramer; individual homodimers associates to form a homotetramer (PubMed:26529540). Homooctamer; individual homodimers associates to form a homooctamer and homooligomerization is required for proper localization to the cell membrane (PubMed:26876602). Heterodimer with PRMT1; heterodimerization may recruit PRMT1 activity to the plasma membrane (PubMed:16051612). Interacts with PRMT2 (via the SH3 domain) (PubMed:17925405). Interacts with FYN (via the SH3 domain) (PubMed:17925405). Interacts with EWS; independently of EWS methylation status (PubMed:18320585). Brain-specific. The SH3-binding motifs mediate the interaction with SH3 domain-containing proteins such as PRMT2 and FYN, possibly leading to displace the N-terminal domain and activate the protein. The N-terminal region (1-60) inhibits the arginine N-methyltransferase activity. Belongs to the class I-like SAM-binding methyltransferase superfamily. Protein arginine N-methyltransferase family. PRMT8 subfamily.