Structure of the YibK methyltransferase fromHaemophilus influenzae (HI0766): A cofactor bound at a site formed by a knot (original) (raw)

Crystal structure of the homocysteine methyltransferase MmuM from Escherichia coli

The Biochemical journal, 2015

Homocysteine S -methyltransferases (HMTs, EC 2.1.1.0) catalyze the conversion of homocysteine to methionine using S -methylmethionine or S -adenosylmethionine as the methyl donor. HMTs play an important role in methionine biosynthesis and are widely distributed among microorganisms, plants, and animals. Additionally, HMTs play a role in metabolite repair of S -adenosylmethionine by removing an inactive diastereomer from the pool. The mmuM gene product from Escherichia coli is an archetypal HMT family protein and contains a predicted Zn-binding motif in the enzyme active site. Here we present X-ray structures for MmuM in oxidized, apo, and metallated forms, representing the first such structures for any member of the HMT family. The structures reveal a metal/substrate binding pocket distinct from those in related enzymes. The presented structure analysis and modelling of co-substrate interactions provide valuable insight into the function of MmuM in both methionine biosynthesis and c...