Substrate Specificity of Human Protein Arginine Methyltransferase 7 (PRMT7): The Importance of Acidic Residues in the Double E Loop [Enzymology]

October 7th, 2014 by Feng, Y., Hadjikyriacou, A., Clarke, S. G.

Protein arginine methyltransferase 7 (PRMT7) methylates arginine residues on various protein substrates and is involved in DNA transcription, RNA splicing, DNA repair, cell differentiation and metastasis. The substrate sequences it recognizes in vivo and the enzymatic mechanism behind it, however, remain to be explored. Here we characterize methylation catalyzed by a bacterially-expressed GST-tagged human PRMT7 fusion protein with a broad range of peptide and protein substrates. After confirming its type III activity generating only ω-NG-monomethylarginine (MMA) and its distinct substrate specificity for RXR motifs surrounded by basic residues, we performed site-directed mutagenesis studies on this enzyme, revealing that two acidic residues within the double E loop, D147 and E149, modulate the substrate preference. Furthermore, altering a single acidic residue E478 on the C-terminal domain to glutamine nearly abolished the activity of the enzyme. Additionally, we demonstrate that PRMT7 has unusual temperature dependence and salt tolerance. These results provide a biochemical foundation to understanding the broad biological functions of PRMT7 in health and disease.
  • Posted in Journal of Biological Chemistry, Publications
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