Fig. 4. Structural determinants for product specificity of Type I, II and III PRMTs. Type I and II PRMTs asymmetrically and symmetrically dimethylate arginine side-chains respectively, while Type III PRMTs mono-methylate only. The conserved “double-E loop” glutamates are shown, along with residues dictating class specificity in the crystal structures of CARM1 [PDB: 2Y1X], PRMT5 [; 4GQB] and TbPRMT7 [; 4M38]. The substrate arginine (positioned manually in the case of CARM1 by superimposing the guanidinium group on the alanine moiety of a co-crystallized inhibitor [; 2Y1X]) is shown in magenta. Orange: residues from the α-helix of CARM1 and TbPRMT7, and from the linker region of PRMT5.
