|Name||Mr. Abhishek Thakur|
|Organization or Institution||University of Miami|
F71I mutation in PRMT7 alters product specificity
Abhishek Thakur1, Betsy Caceres2, Joan M. Hevel2, Orlando Acevedo1
1Department of Chemistry, University of Miami, Coral Gables, FL 33146.
Protein arginine methylation is an important post-translational modification involved in cellular processes, RNA processing, and gene transcription. Apart from this, overexpression of PRMTs have shown to be associated with different types of cancer. The arginine methylation enzyme of interest, protein arginine methyltransferase 7 (PRMT7), exclusively generates the first turnover product, monomethylated arginine (MMA), but neither of the second turnover products, asymmetric dimethylated arginine (ADMA) and symmetric dimethylated arginine (SDMA). However, it remains unclear how PRMT7 product specificity is regulated and which active site base governs the proton abstraction in the SN2 mechanism. Computational and experimental mutagenesis work has been performed and it was determined that single amino acid mutations, i.e., Phe71Ile, in the PRMT7 active site can enable the enzyme to perform a second turnover and that Glu172 might be acting as the base. Whereas mutating Phe71Ala and Phe71Ser could not yield the second turnover. Combined quantum mechanical and molecular mechanical calculations and molecular dynamics simulations (QM/MM/MD) that employed free energy perturbation methods have been used to help elucidate the origin of the product specificity in both WT and mutant PRMT7 enzymes. Additional binding pocket volume directing product specificity for the PRMT7 system were investigated and discussed.