Protein arginine methyltransferases (PRMTs) play important roles in both noraml physiology and human diseases. Deregulation of PRMT activity has been linked to several pathological states such as cancer (sic) cardiovascular disorders. Herein, we report our work of designing and using new fluorescent reporter to perform single-stp analysis of substrate binding and methylation by PRMT1. Both fluorescence (sic) and anisotropy of the two reporters, R4-FL and H4-FL, were shown to effectively maifest enzyme-(sic) strate interaction, highlighting their application in investigating PRMT inhibitors. In particular, (sic) methylation process of R4-FL can be directly studied using fluorescence intensity readout. By combining the fluorescent measurement with radioactive analysis, we determined that AMl-1 inhibits PRMT1 activity through the mechanism of blocking peptide substrate binding. (C) 2008 Elsevier Ince. All rights reserved.