Abstract
Isocitrate dehydrogenase is a catabolic enzyme that acts during the third step of the tricarboxylic acid cycle. The hypothetical protein ST2166 from the archaeon Sulfolobus tokodaii was isolated and crystallized. It shares high primary structure homology with prokaryotic NADP+-dependent IDHs, suggesting that these enzymes share a common enzymatic mechanism. The crystal structure of ST2166 was determined at 2.0 Å resolution in the apo form, and then the structure of the crystal soaked with NADP+ was also determined at 2.4 Å resolution, which contained NADP+ bound at the putative active site. Comparisons between the structures of apo and NADP+-bound forms and NADP-IDHs from other prokaryotes suggest that prokaryotic NADP-IDHs recognize their cofactors using conserved Lys335, Tyr336, and Arg386 in ST2166 at the opening cleft before the domain closure.
Highlights
Isocitrate dehydrogenase (IDH) catalyzes the oxidative decarboxylation of isocitrate to produce α-ketoglutarate daninduCclOeo2tiwdehil(ephreodsupchiantge)th(eNcAoDfa(cPto)+r)nticootNinAamD(idPe)Hadeunsiinnge divalent metal cation (Mg2+ or Mn2+) in the tricarboxylic acid cycle
The catalytic activity of EcIDH is regulated by bifunctional enzyme IDH kinase/phosphatase (AceK) by phosphorylation/dephosphorylation of Ser113 in the loop near the active site [2, 10]
ST2166 crystallized in a monoclinic crystal belonging to P21 that diffracted X-rays up to 2.0 Å resolution
Summary
Isocitrate dehydrogenase (IDH) catalyzes the oxidative decarboxylation of isocitrate to produce α-ketoglutarate daninduCclOeo2tiwdehil(ephreodsupchiantge)th(eNcAoDfa(cPto)+r)nticootNinAamD(idPe)Hadeunsiinnge divalent metal cation (Mg2+ or Mn2+) in the tricarboxylic acid cycle. The amino acid sequence identity between subfamilies I and II is low (
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