Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe crystal structure of Acidithiobacillus thiooxidans isocitrate dehydrogenase complexed with NAD+ and citrate has been solved to a resolution of 1.9 A. The protein fold of this NAD+-dependent enzyme shares a high similarity with those of NADP+-dependent bacterial ICDHs. The NAD+ and the citrate are clearly identified in the active site cleft with a well-defined electron density. Asp-357 is the direct cofactor-specificity determinant that interacts with 2'-OH and 3'-OH of the adenosine ribose. The adenosine ribose takes a C2'-endo puckering conformation as previously reported for an NAD+-specific isopropylmalate dehydrogenase. The nicotinamide moiety of NAD+ has the amide NH2 group oriented in cis conformation with respect to the C4 carbon of the nicotinamide ring, slanted toward the bound citrate molecule with a dihedral angle of -21 degrees . The semi-empirical molecular orbital calculation suggests that the pro-R hydrogen atom at C4 of NADH would bear the largest negative charge when the amide NH2 group is in such conformation, suggesting that the amide group has a catalytically significant role in stabilizing the transition state as NADH is being formed during the hydride transfer catalysis. Structure and quantum chemical analysis of NAD+-dependent isocitrate dehydrogenase: hydride transfer and co-factor specificity.,Imada K, Tamura T, Takenaka R, Kobayashi I, Namba K, Inagaki K Proteins. 2008 Jan 1;70(1):63-71. PMID:17634983[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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