Protein arginine methyltransferase 7 has a novel homodimer-like structure formed by tandem repeats

• CePRMT7 is a member of PRMT7 subfamily and harbors two tandem repeated PRMT core domains.
• The crystal structure of PRMT7 in complex with SAH was determined.
• A single PRMT7 molecule forms a homodimer-like arrangement.
• The structural features strongly suggest that PRMT7 functions as a type III enzyme.

Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyze the transfer of methyl groups from S-adenosyl-l-methionine to nitrogen atoms on arginine residues. Here, we describe the crystal structure of Caenorhabditis elegans PRMT7 in complex with its reaction product S-adenosyl-l-homocysteine. The structural data indicated that PRMT7 harbors two tandem repeated PRMT core domains that form a novel homodimer-like structure. S-adenosyl-l-homocysteine bound to the N-terminal catalytic site only; the C-terminal catalytic site is occupied by a loop that inhibits cofactor binding. Mutagenesis demonstrated that only the N-terminal catalytic site of PRMT7 is responsible for cofactor binding.