Crystal structures of the quinone oxidoreductase from Thermus thermophilus HB8 and its complex with NADPH: Implication for NADPH and substrate recognition

Yoshimitsu Shimomura, Yoshimitsu Kakuta, Keiichi Fukuyama

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

The crystal structures of the ζ-crystalline-like soluble quinone oxidoreductase from Thermus thermophilus HB8 (QORTt) and of its complex with NADPH have been determined at 2.3- and 2.8-Å resolutions, respectively. QORTt is composed of two domains, and its overall fold is similar to the folds of Escherichia coli quinone oxidoreductase (QOREc) and horse liver alcohol dehydrogenase. QORTt forms a homodimer in the crystal by interaction of the βF-strands in domain II, forming a large β-sheet that crosses the dimer interface. High thermostability of QORTt was evidenced by circular dichroic measurement. NADPH is located between the two domains in the QORTt-NADPH complex. The disordered segment involved in the coenzyme binding of apo-QORTt 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 QORTt, suggesting that QORTt binds NADPH more readily than NADH. The putative substrate-binding site of QORTt unlike that of QOREc, is largely blocked by nearby residues, permitting access only to small substrates. This may explain why QORTt has weak p-benzoquinone reduction activity and is inactive with such large substrates of QOREc as 5-hydroxy-1,4-naphthoquinone and phenanthraquinone.

Original languageEnglish
Pages (from-to)4211-4218
Number of pages8
JournalJournal of bacteriology
Volume185
Issue number14
DOIs
Publication statusPublished - Jul 2003

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

Fingerprint Dive into the research topics of 'Crystal structures of the quinone oxidoreductase from Thermus thermophilus HB8 and its complex with NADPH: Implication for NADPH and substrate recognition'. Together they form a unique fingerprint.

Cite this