1MSK

METHIONINE SYNTHASE (ACTIVATION DOMAIN)

Summary for 1MSK

• Entry DOI: 10.2210/pdb1msk/pdb
• Descriptor: COBALAMIN-DEPENDENT METHIONINE SYNTHASE, ACETATE ION, S-ADENOSYLMETHIONINE, ... (4 entities in total)
• Functional Keywords: methyltransferase, transferase, methionine biosynthesis, vitamin b12
• Biological source: Escherichia coli K12
• Total number of polymer chains: 1
• Total formula weight: 38206.65

Authors

Dixon, M.M.,Huang, S.,Matthews, R.G.,Ludwig, M.L. (deposition date: 1996-08-03, release date: 1997-04-01, Last modification date: 2024-02-14)

Primary citation

Dixon, M.M.,Huang, S.,Matthews, R.G.,Ludwig, M.
The structure of the C-terminal domain of methionine synthase: presenting S-adenosylmethionine for reductive methylation of B12.
Structure, 4:1263-1275, 1996

PubMed Abstract: In both mammalian and microbial species, B12-dependent methionine synthase catalyzes methyl transfer from methyltetrahydrofolate (CH3-H4folate) to homocysteine. The B12 (cobalamin) cofactor plays an essential role in this reaction, accepting the methyl group from CH3-H4folate to form methylcob(III)alamin and in turn donating the methyl group to homocysteine to generate methionine and cob(I)alamin. Occasionally the highly reactive cob(I)alamin intermediate is oxidized to the catalytically inactive cob(II)alamin form. Reactivation to sustain enzyme activity is achieved by a reductive methylation, requiring S-adenosylmethionine (AdoMet) as the methyl donor and, in Esherichia coli, flavodoxin as an electron donor. The intact system is controlled and organized so that AdoMet, rather than methyltetrahydrofolate, is the methyl donor in the reactivation reaction. AdoMet is not wasted as a methyl donor in the catalytic cycle in which methionine is synthesized from homocysteine. The structures of the AdoMet binding site and the cobalamin-binding domains (previously determined) provide a starting point for understanding the methyl transfer reactions of methionine synthase.

PubMed: 8939751
DOI: 10.1016/S0969-2126(96)00135-9

Experimental method

X-RAY DIFFRACTION (1.8 Å)