1u1h
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A. thaliana cobalamine independent methionine synthase
OverviewOverview
Cobalamin-independent methionine synthase (MetE) catalyzes the synthesis, of methionine by a direct transfer of the methyl group of, N5-methyltetrahydrofolate (CH3-H2PteGlun) to the sulfur atom of, homocysteine (Hcy). We report here the first crystal structure of this, metalloenzyme under different forms, free or complexed with the Hcy and, folate substrates. The Arabidopsis thaliana MetE (AtMetE) crystals reveal, a monomeric structure built by two (betaalpha)8 barrels making a deep, groove at their interface. The active site is located at the surface of, the C-terminal domain, facing the large interdomain cleft. Inside the, active site, His647, Cys649, and Cys733 are involved in zinc coordination, whereas Asp605, Ile437, and Ser439 interact with Hcy. Opposite the, zinc/Hcy binding site, a cationic loop (residues 507-529) belonging to the, C-terminal domain anchors the first glutamyl residue of CH3-H4PteGlu5. The, pterin moiety of CH3-H4PteGlu5 is stacked with Trp567, enabling the, N5-methyl group to protrude in the direction of the zinc atom. These data, suggest a structural role of the N-terminal domain of AtMetE in the, stabilization of loop 507-529 and in the interaction with the, poly-glutamate chain of CH3-H4PteGlun. Comparison of AtMetE structures, reveals that the addition of Hcy does not lead to a direct coordination of, the sulfur atom with zinc but to a reorganization of the zinc binding site, with a stronger coordination to Cys649, Cys733, and a water molecule.
About this StructureAbout this Structure
1U1H is a Single protein structure of sequence from Arabidopsis thaliana with ZN, SO4 and MET as ligands. Active as 5-methyltetrahydropteroyltriglutamate--homocysteine S-methyltransferase, with EC number 2.1.1.14 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of cobalamin-independent methionine synthase complexed with zinc, homocysteine, and methyltetrahydrofolate., Ferrer JL, Ravanel S, Robert M, Dumas R, J Biol Chem. 2004 Oct 22;279(43):44235-8. Epub 2004 Aug 23. PMID:15326182
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