Human HMT1 hnRNP methyltransferase-like 3

Protein arginine methylation is a common posttranslational modification process in eukayotes.
There are two major types of protein arginine methyltransferases (PRMTs) that transfer the methyl group from S-adenosyl-L-methionine (SAM) to the guanidino group of arginine in protein substrates.
Both groups of PRMTs catalyze the formation of monomethyl-arginine but differ in the dimethylation products: type I PRMTs form asymmetric dimethylarginine; type II PRMTs form symmetric dimethylarginine.
The posttranslational methylation of arginine residues has been shown to modify protein function by regulating protein-protein interactions. Arginine methylation is involved in a number of processes such as DNA repair, RNA transcription, signal transduction, protein compartmentalization.
We have solved the crystal structure of human HMT1 hnRNP methyltransferase-like 3 (HRMT1L3) protein in complex with S-adenosyl-L-homocysteine (SAH) at 2.0 Å resolution.
Human HRMT1L3 is a cytosolic type I PRMT.
It methylates arginine residues in 40S ribosomal protein S2 and affects the relative level of ribosomal subunits.
Our structure revealed a core fold different from a typical SAM-dependent methyltransferase.
It provides important information for understanding of catalytic mechanism of PRMTs.