Structural highlights
Function[METH_ECOLI] Catalyzes the transfer of a methyl group from methyl-cobalamin to homocysteine, yielding enzyme-bound cob(I)alamin and methionine. Subsequently, remethylates the cofactor using methyltetrahydrofolate. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedB(12)-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that uses bound cobalamin as an intermediate methyl carrier. Major domain rearrangements have been postulated to explain how cobalamin reacts with three different substrates: homocysteine, methyltetrahydrofolate and S-adenosylmethionine (AdoMet). Here we describe the 3.0 A structure of a 65 kDa C-terminal fragment of MetH that spans the cobalamin- and AdoMet-binding domains, arranged in a conformation suitable for the methyl transfer from AdoMet to cobalamin that occurs during activation. In the conversion to the activation conformation, a helical domain that capped the cofactor moves 26 A and rotates by 63 degrees, allowing formation of a new interface between cobalamin and the AdoMet-binding (activation) domain. Interactions with the MetH activation domain drive the cobalamin away from its binding domain in a way that requires dissociation of the axial cobalt ligand and, thereby, provide a mechanism for control of the distribution of enzyme conformations. Domain alternation switches B(12)-dependent methionine synthase to the activation conformation.,Bandarian V, Pattridge KA, Lennon BW, Huddler DP, Matthews RG, Ludwig ML Nat Struct Biol. 2002 Jan;9(1):53-6. PMID:11731805[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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