3BUL
E. coli I690C/G743C MetH C-terminal fragment (649-1227)
Summary for 3BUL
| Entry DOI | 10.2210/pdb3bul/pdb |
| Related | 1K7Y |
| Descriptor | Methionine synthase, COBALAMIN (3 entities in total) |
| Functional Keywords | meth, transferase, reactivation conformation, h759, cobalamin, intermodular interactions, amino-acid biosynthesis, cobalt, metal-binding, methionine biosynthesis, methyltransferase, s-adenosyl-l-methionine |
| Biological source | Escherichia coli |
| Total number of polymer chains | 1 |
| Total formula weight | 66505.86 |
| Authors | Koutmos, M.,Pattridge, K.A.,Ludwig, M.L. (deposition date: 2008-01-03, release date: 2008-04-01, Last modification date: 2024-10-30) |
| Primary citation | Datta, S.,Koutmos, M.,Pattridge, K.A.,Ludwig, M.L.,Matthews, R.G. A disulfide-stabilized conformer of methionine synthase reveals an unexpected role for the histidine ligand of the cobalamin cofactor. Proc.Natl.Acad.Sci.Usa, 105:4115-4120, 2008 Cited by PubMed Abstract: B(12)-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that is alternately methylated by methyltetrahydrofolate to form methylcobalamin and demethylated by homocysteine to form cob(I)alamin. Major domain rearrangements are required to allow cobalamin to react with three different substrates: homocysteine, methyltetrahydrofolate, and S-adenosyl-l-methionine (AdoMet). These same rearrangements appear to preclude crystallization of the wild-type enzyme. Disulfide cross-linking was used to lock a C-terminal fragment of the enzyme into a unique conformation. Cysteine point mutations were introduced at Ile-690 and Gly-743. These cysteine residues span the cap and the cobalamin-binding module and form a cross-link that reduces the conformational space accessed by the enzyme, facilitating protein crystallization. Here, we describe an x-ray structure of the mutant fragment in the reactivation conformation; this conformation enables the transfer of a methyl group from AdoMet to the cobalamin cofactor. In the structure, the axial ligand to the cobalamin, His-759, dissociates from the cobalamin and forms intermodular contacts with residues in the AdoMet-binding module. This unanticipated intermodular interaction is expected to play a major role in controlling the distribution of conformers required for the catalytic and the reactivation cycles of the enzyme. PubMed: 18332423DOI: 10.1073/pnas.0800329105 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.3 Å) |
Structure validation
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