2iu0

crystal structures of transition state analogue inhibitors of inosine monophosphate cyclohydrolase

spinqualitylabelsall models 2iu0, resolution 2.53Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2iu0 is a 2 chain structure with sequence from Gallus gallus. This structure supersedes the now removed PDB entry 2b0w. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: 203, K Resources: FirstGlance, OCA, RCSB, PDBsum Function [PUR9_CHICK] Bifunctional enzyme that catalyzes 2 steps in purine biosynthesis. 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 PubMed The inosine monophosphate cyclohydrolase (IMPCH) component (residues 1-199) of the bifunctional enzyme aminoimidazole-4-carboxamide ribonucleotide transformylase (AICAR Tfase, residues 200-593)/IMPCH (ATIC) catalyzes the final step in the de novo purine biosynthesis pathway that produces IMP. As a potential target for antineoplastic intervention, we designed IMPCH inhibitors, 1,5-dihydroimidazo[4,5-c][1,2,6]thiadiazin-4(3H)-one 2,2-dioxide (heterocycle, 1), the corresponding nucleoside (2), and the nucleoside monophosphate (nucleotide) (3), as mimics of the tetrahedral intermediate in the cyclization reaction. All compounds are competitive inhibitors against IMPCH (K(i) values = 0.13-0.23 microm) with the simple heterocycle 1 exhibiting the most potent inhibition (K(i) = 0.13 microm). Crystal structures of bifunctional ATIC in complex with nucleoside 2 and nucleotide 3 revealed IMPCH binding modes similar to that of the IMPCH feedback inhibitor, xanthosine 5'-monophosphate. Surprisingly, the simpler heterocycle 1 had a completely different IMPCH binding mode and was relocated to the phosphate binding pocket that was identified from previous xanthosine 5'-monophosphate structures. The aromatic imidazole ring interacts with a helix dipole, similar to the interaction with the phosphate moiety of 3. The crystal structures not only revealed the mechanism of inhibition of these compounds, but they now serve as a platform for future inhibitor improvements. Importantly, the nucleoside-complexed structure supports the notion that inhibitors lacking a negatively charged phosphate can still inhibit IMPCH activity with comparable potency to phosphate-containing inhibitors. Provocatively, the nucleotide inhibitor 3 also binds to the AICAR Tfase domain of ATIC, which now provides a lead compound for the design of inhibitors that simultaneously target both active sites of this bifunctional enzyme. Structure-based design, synthesis, evaluation, and crystal structures of transition state analogue inhibitors of inosine monophosphate cyclohydrolase.,Xu L, Chong Y, Hwang I, D'Onofrio A, Amore K, Beardsley GP, Li C, Olson AJ, Boger DL, Wilson IA J Biol Chem. 2007 Apr 27;282(17):13033-46. Epub 2007 Feb 26. PMID:17324932 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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