1umy
From Proteopedia
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BHMT FROM RAT LIVER
Overview
Betaine homocysteine S-methyltransferase (BHMT) is one of the two enzymes, known to methylate homocysteine to generate methionine in the liver. It, presents a Zn(2+) atom linked to three essential Cys residues. The crystal, structure of rat liver BHMT has been solved at 2.5A resolution, using, crystals with P2(1) symmetry and 45% solvent content in the cell. The, asymmetric unit contains the whole functional tetramer showing point, symmetry 222. The overall fold of the subunit consists mostly of a, (alpha/beta)(8) barrel, as for human BHMT. From the end of the barrel, the, polypeptide chain extends away and makes many interactions with a, different subunit, forming tight dimers. The most remarkable structural, feature of rat liver BHMT is the presence of a helix including residues, 381-407, at the C terminus of the chain, which bind together the dimers AB, to CD. A strong ion-pair and more than 60 hydrophobic interactions keep, this helix stacked to the segment 316-349 from the opposite subunit., Moreover, the crystal structure of free rat liver BHMT clearly shows that, Tyr160 is the fourth ligand coordinated to Zn, which is replaced by Hcy, upon binding. Two residues essential for substrate recognition, Phe76 and, Tyr77, are provided by a conformational change in a partially disordered, loop (L2). The crucial role of these residues is highlighted by, site-directed mutagenesis.
About this Structure
1UMY is a Single protein structure of sequence from [1] with and as ligands. Active as Betaine--homocysteine S-methyltransferase, with EC number 2.1.1.5 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Crystal structure of rat liver betaine homocysteine s-methyltransferase reveals new oligomerization features and conformational changes upon substrate binding., Gonzalez B, Pajares MA, Martinez-Ripoll M, Blundell TL, Sanz-Aparicio J, J Mol Biol. 2004 May 7;338(4):771-82. PMID:15099744
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