2b0t
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(New page: 200px<br /><applet load="2b0t" size="450" color="white" frame="true" align="right" spinBox="true" caption="2b0t, resolution 1.75Å" /> '''Structure of Monomer...)
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Revision as of 06:23, 21 November 2007
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Structure of Monomeric NADP Isocitrate dehydrogenase
Overview
Both monomeric and dimeric NADP+-dependent isocitrate dehydrogenase (IDH), belong to the metal-dependent beta-decarboxylating dehydrogenase family, and catalyze the oxidative decarboxylation from 2R,3S-isocitrate to yield, 2-oxoglutarate, CO2, and NADPH. It is important to solve the structures of, IDHs from various species to correlate with its function and evolutionary, significance. So far, only two crystal structures of, substrate/cofactor-bound (isocitrate/NADP) NADP+-dependent monomeric IDH, from Azotobacter vinelandii (AvIDH) have been solved. Herein, we report, for the first time the substrate/cofactor-free structure of a monomeric, NADP+-dependent IDH from Corynebacterium glutamicum (CgIDH) in the, presence of Mg2+. The 1.75 A structure of CgIDH-Mg2+ showed a distinct, open conformation in contrast to the closed conformation of, AvIDH-isocitrate/NADP+ complexes. Fluorescence studies on CgIDH in the, presence of isocitrate/or NADP+ suggest the presence of low energy barrier, conformers. In CgIDH, the amino acid residues corresponding to the, Escherichia coli IDH phosphorylation-loop are alpha-helical compared with, the more flexible random-coil region in the E. coli protein where IDH, activation is controlled by phosphorylation. This more structured region, supports the idea that activation of CgIDH is not controlled by, phosphorylation. Monomeric NADP+-specific IDHs have been identified from, about 50 different bacterial species, such as proteobacteria, actinobacteria, and planctomycetes, whereas, dimeric NADP+-dependent IDHs, are diversified in both prokaryotes and eukaryotes. We have constructed a, phylogenetic tree based on amino acid sequences of all bacterial monomeric, NADP+-dependent IDHs and also another one with specifically chosen species, which either contains both monomeric and dimeric NADP+-dependent IDHs or, have monomeric NADP+-dependent, as well as NAD+-dependent IDHs. This is, done to examine evolutionary relationships.
About this Structure
2B0T is a Single protein structure of sequence from Corynebacterium glutamicum with MG as ligand. Active as Isocitrate dehydrogenase (NADP(+)), with EC number 1.1.1.42 Full crystallographic information is available from OCA.
Reference
Substrate-free structure of a monomeric NADP isocitrate dehydrogenase: an open conformation phylogenetic relationship of isocitrate dehydrogenase., Imabayashi F, Aich S, Prasad L, Delbaere LT, Proteins. 2006 Apr 1;63(1):100-12. PMID:16416443
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