1iyz
From Proteopedia
Crystal Structures of the Quinone Oxidoreductase from Thermus thermophilus HB8 and Its Complex with NADPH
Overview
The crystal structures of the zeta-crystalline-like soluble quinone oxidoreductase from Thermus thermophilus HB8 (QOR(Tt)) and of its complex with NADPH have been determined at 2.3- and 2.8-A resolutions, respectively. QOR(Tt) is composed of two domains, and its overall fold is similar to the folds of Escherichia coli quinone oxidoreductase (QOR(Ec)) and horse liver alcohol dehydrogenase. QOR(Tt) forms a homodimer in the crystal by interaction of the betaF-strands in domain II, forming a large beta-sheet that crosses the dimer interface. High thermostability of QOR(Tt) was evidenced by circular dichroic measurement. NADPH is located between the two domains in the QOR(Tt)-NADPH complex. The disordered segment involved in the coenzyme binding of apo-QOR(Tt) becomes ordered upon NADPH binding. The segment covers an NADPH-binding cleft and may serve as a lid. The 2'-phosphate group of the adenine of NADPH is surrounded by polar and positively charged residues in QOR(Tt), suggesting that QOR(Tt) binds NADPH more readily than NADH. The putative substrate-binding site of QOR(Tt), unlike that of QOR(Ec), is largely blocked by nearby residues, permitting access only to small substrates. This may explain why QOR(Tt) has weak p-benzoquinone reduction activity and is inactive with such large substrates of QOR(Ec) as 5-hydroxy-1,4-naphthoquinone and phenanthraquinone.
About this Structure
1IYZ is a Single protein structure of sequence from Thermus thermophilus. Full crystallographic information is available from OCA.
Reference
Crystal structures of the quinone oxidoreductase from Thermus thermophilus HB8 and its complex with NADPH: implication for NADPH and substrate recognition., Shimomura Y, Kakuta Y, Fukuyama K, J Bacteriol. 2003 Jul;185(14):4211-8. PMID:12837796 Page seeded by OCA on Fri May 2 20:36:15 2008
