A Kinetic Study of Human Protein Arginine N-Methyltransferase 6 Reveals a Distributive Mechanism

Human protein arginine N-methyltransferase 6 (PRMT6) transfers methyl groups from the co-substrate S-adenosyl-l-methionine to arginine residues within proteins, forming S-adenosyl-l-homocysteine as well as ω-NG-monomethylarginine (MMA) and asymmetric dimethylarginine (aDMA) residues in the process....

Full description

Saved in:

Bibliographic Details
Published in:	The Journal of biological chemistry 2008-04, Vol.283 (15), p.10015-10025
Main Authors:	Lakowski, Ted M., Frankel, Adam
Format:	Article
Language:	eng
Subjects:	Arginine - chemistry Arginine - genetics Arginine - metabolism Humans Kinetics Methylation Nuclear Proteins - chemistry Nuclear Proteins - genetics Nuclear Proteins - metabolism Peptides - chemistry Peptides - genetics Peptides - metabolism Protein Binding - physiology Protein Processing, Post-Translational - physiology Protein-Arginine N-Methyltransferases - chemistry Protein-Arginine N-Methyltransferases - genetics Protein-Arginine N-Methyltransferases - metabolism Recombinant Fusion Proteins - chemistry Recombinant Fusion Proteins - genetics Recombinant Fusion Proteins - metabolism S-Adenosylhomocysteine - chemistry S-Adenosylhomocysteine - metabolism S-Adenosylmethionine - chemistry S-Adenosylmethionine - genetics S-Adenosylmethionine - metabolism Substrate Specificity - physiology
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Human protein arginine N-methyltransferase 6 (PRMT6) transfers methyl groups from the co-substrate S-adenosyl-l-methionine to arginine residues within proteins, forming S-adenosyl-l-homocysteine as well as ω-NG-monomethylarginine (MMA) and asymmetric dimethylarginine (aDMA) residues in the process. We have characterized the kinetic mechanism of recombinant His-tagged PRMT6 using a mass spectrometry method for monitoring the methylation of a series of peptides bearing a single arginine, MMA, or aDMA residue. We find that PRMT6 follows an ordered sequential mechanism in which S-adenosyl-l-methionine binds to the enzyme first and the methylated product is the first to dissociate. Furthermore, we find that the enzyme displays a preference for the monomethylated peptide substrate, exhibiting both lower Km and higher Vmax values than what are observed for the unmethylated peptide. This difference in substrate Km and Vmax, as well as the lack of detectable aDMA-containing product from the unmethylated substrate, suggest a distributive rather than processive mechanism for multiple methylations of a single arginine residue. In addition, we speculate that the increased catalytic efficiency of PRMT6 for methylated substrates combined with lower Km values for native protein methyl acceptors may obscure this distributive mechanism to produce an apparently processive mechanism.
ISSN:	0021-9258 1083-351X