Arginine methylation is a common posttranslational modification found on nuclear and cytoplasmic proteins that has roles in transcriptional regulation, RNA metaboolism and DNA repair. The protozoan parasite Toxoplasma gondii has a complex life cycle requiring transcriptional plasticity and has unique transcriptional regulatory pathways. Arginine methylation probably plays an important part in transcriptional regulation and splicing biology in this organism. The T. gondii genome contains five putative protein arginine methyltransferases (PRMTs), of which PRMT1 is important for cell division and growth. In order to better understand the functions of the post translational modifiction monomethyl arginine (MMA) in T. gondii we performed a proteomic analysis of monomethyl arginine (MMA) proteins in wild type and PRMT1 knockout parasites using affinity purification employing anti-MMA specific antibodies followed by mass spectrometry.