PRMT1: ProductsPRMT/PRMT1 (Protein-Arginine Methyltransferase 1; also HRMT1L2 and HMT2) is a 42-45 kDa type I member of the arginine N-methyltransferase family of enzymes. It is ubiquitously expressed and dimethylates single arginine residue nitrogen atoms in a distributive manner (i.e.-with substrate release following each methlyation step). PRMT1 forms homodimers, and heterodimers with PRMT3, and exists as part of a 300-400 kDa complex in vivo. Human PRMT1 is 361 amino acids in length and contains one adenosyl-L-methionine binding site (aa 85-153) and a phosphorylation site at Tyr299. There are multiple splice variants that show distinct substrate specificities. There is an alternate start site 10 aa upstream of the standard start site, and a single Met, plus a five aa and 11 aa substiuition for aa 1-19. One isoform has a 2 aa substitution for aa 1-20 accompanied by a deketion of aa 52-67. Over aa 218-361, human PRMT1 is 100% identical in aa sequence to mouse PRMT1.