1b3o
TERNARY COMPLEX OF HUMAN TYPE-II INOSINE MONOPHOSPHATE DEHYDROGENASE WITH 6-CL-IMP AND SELENAZOLE ADENINE DINUCLEOTIDE
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| , resolution 2.90Å | |||||||
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| Ligands: | , and | ||||||
| Activity: | IMP dehydrogenase, with EC number 1.1.1.205 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
OverviewOverview
Inosine monophosphate dehydrogenase (IMPDH) controls a key metabolic step in the regulation of cell growth and differentiation. This step is the NAD-dependent oxidation of inosine 5' monophosphate (IMP) to xanthosine 5' monophosphate, the rate-limiting step in the synthesis of the guanine nucleotides. Two isoforms of IMPDH have been identified, one of which (type II) is significantly up- regulated in neoplastic and differentiating cells. As such, it has been identified as a major target in antitumor and immunosuppressive drug design. We present here the 2.9-A structure of a ternary complex of the human type II isoform of IMPDH. The complex contains the substrate analogue 6-chloropurine riboside 5'-monophosphate (6-Cl-IMP) and the NAD analogue selenazole-4-carboxamide adenine dinucleotide, the selenium derivative of the active metabolite of the antitumor drug tiazofurin. The enzyme forms a homotetramer, with the dinucleotide binding at the monomer-monomer interface. The 6 chloro-substituted purine base is dehalogenated, forming a covalent adduct at C6 with Cys-331. The dinucleotide selenazole base is stacked against the 6-Cl-IMP purine ring in an orientation consistent with the B-side stereochemistry of hydride transfer seen with NAD. The adenosine end of the ligand interacts with residues not conserved between the type I and type II isoforms, suggesting strategies for the design of isoform-specific agents.
About this StructureAbout this Structure
1B3O is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of human type II inosine monophosphate dehydrogenase: implications for ligand binding and drug design., Colby TD, Vanderveen K, Strickler MD, Markham GD, Goldstein BM, Proc Natl Acad Sci U S A. 1999 Mar 30;96(7):3531-6. PMID:10097070
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