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. Able to mono- and dimethylate EWS protein; however its precise role toward EWS remains unclear as it still interacts with fully methylated EWS. 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. Tetramer; individual homodimers associates to form a homotetramer. Homooctamer; individual homodimers associates to form a homooctamer and homooligomerization is required for proper localization to the cell membrane. Heterodimer with PRMT1; heterodimerization may recruit PRMT1 activity to the plasma membrane. Interacts with PRMT2 (via the SH3 domain). Interacts with FYN (via the SH3 domain). Interacts with EWS; independently of EWS methylation status. Brain-specific. Only expressed in neurons, especially in the somatosensory and limbic systems, and a part of motor system. Highly expressed in all of the regions related to general somatosensory system. Expressed in most of the relay nuclei intervening the special somatosensory system, such as the auditory, visual and vestibular systems. Also present in forebrain limbic areas and thalamic nuclei relevant to limbic areas and in areas related to the motor system, such as the caudate putamen, Purkinje cells, inferior olivary nucleus and cerebellar nuclei. 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.