PROSITE documentation PDOC50974
AdoMet activation domain profile


Prokaryotic and eukaryotic B12-dependent methionine synthase (MetH) (EC is a large, modular protein that catalyses the transfer of a methyl group from methyltetrahydrofolate (CH3-H4folate) to homocysteine (Hcy) to form methionine, using cobalamin as an intermediate methyl carrier. MetH enzymes consist of four functional modules arranged in a linear fashion with single interdomain connectors. The N-terminal Hcy domain (see <PDOC50970>) utilizes a Zn(Cys)3 cluster to bind and activate Hcy, the second module, the pterin-binding domain (see <PDOC50972>), activates methyltetrahydrofolate (CH3-H4folate) for methyl transfer, and the third module binds cobalamin. The fourth C-terminal module binds S-adenosylmethionine (AdoMet, or SAM) and is required for reductive activation. The ~330-residue AdoMet activation domain of MetH is a C-shaped single domain whose central feature is a bent antiparallel β-sheet (see <PDB:1MSK>. The AdoMet ligand binds to the domain near the center of the inner face of the 'C' and is held in place by both side chain and backbone interactions. The three-dimensional structure of the AdoMet activation domain of MetH is unlike any of the recently determined AdoMet-dependent DNA- and RNA-methyltransferases or the catechol O-methyltransferase [1].

The profile we developed covers the entire AdoMet activation domain.

Last update:

May 2004 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

ADOMET_ACTIVATION, PS50974; AdoMet activation domain profile  (MATRIX)


1AuthorsDixon M.M. Huang S. Matthews R.G. Ludwig M.
TitleThe structure of the C-terminal domain of methionine synthase: presenting S-adenosylmethionine for reductive methylation of B12.
SourceStructure 4:1263-1275(1996).
PubMed ID8939751

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