2hsd
From Proteopedia
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THE REFINED THREE-DIMENSIONAL STRUCTURE OF 3ALPHA,20BETA-HYDROXYSTEROID DEHYDROGENASE AND POSSIBLE ROLES OF THE RESIDUES CONSERVED IN SHORT-CHAIN DEHYDROGENASES
Overview
BACKGROUND: Bacterial 3 alpha,20 beta-hydroxysteroid dehydrogenase, reversibly oxidizes the 3 alpha and 20 beta hydroxyl groups of steroids, derived from androstanes and pregnanes. It was the first short-chain, dehydrogenase to be studied by X-ray crystallography. The previous, description of the structure of this enzyme, at 2.6 A resolution, did not, permit unambiguous assignment of several important groups. We have further, refined the structure of the complex of the enzyme with its cofactor, nicotinamide adenine dinucleotide (NAD), and solvent molecules, at the, same resolution. RESULTS: The asymmetric unit of the crystal contains four, monomers, each with 253 amino acid residues, 38 water molecules, and 176, cofactor atoms belonging to four NAD molecules--one for each subunit. The, positioning of the cofactor molecule has been modified from our previous, model and is deeper in the catalytic cavity as observed for other members, of both the long-chain and short-chain dehydrogenase families. The, nicotinamide-ribose end of the cofactor has several possible conformations, or is dynamically disordered. CONCLUSIONS: The catalytic site contains, residues Tyr152 and Lys156. These two amino acids are strictly conserved, in the short-chain dehydrogenase superfamily. Modeling studies with a, cortisone molecule in the catalytic site suggest that the Tyr152, Lys156, and Ser139 side chains promote electrophilic attack on the (C20-O), carbonyl oxygen atom, thus enabling the carbon atom to accept a hydride, from the reduced cofactor.
About this Structure
2HSD is a Single protein structure of sequence from Streptomyces exfoliatus with NAD as ligand. This structure superseeds the now removed PDB entry 1HSD. Active as 3-alpha-(or 20-beta)-hydroxysteroid dehydrogenase, with EC number 1.1.1.53 Full crystallographic information is available from OCA.
Reference
The refined three-dimensional structure of 3 alpha,20 beta-hydroxysteroid dehydrogenase and possible roles of the residues conserved in short-chain dehydrogenases., Ghosh D, Wawrzak Z, Weeks CM, Duax WL, Erman M, Structure. 1994 Jul 15;2(7):629-40. PMID:7922040
Page seeded by OCA on Wed Nov 21 11:56:59 2007
