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| {{STRUCTURE_1lrt| PDB=1lrt | SCENE= }} | | {{STRUCTURE_1lrt| PDB=1lrt | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF TERNARY COMPLEX OF TRITRICHOMONAS FOETUS INOSINE-5'-MONOPHOSPHATE DEHYDROGENASE: STRUCTURAL CHARACTERIZATION OF NAD+ SITE IN MICROBIAL ENZYME'''
| | ===CRYSTAL STRUCTURE OF TERNARY COMPLEX OF TRITRICHOMONAS FOETUS INOSINE-5'-MONOPHOSPHATE DEHYDROGENASE: STRUCTURAL CHARACTERIZATION OF NAD+ SITE IN MICROBIAL ENZYME=== |
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| ==Overview==
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| Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes the conversion of IMP to XMP with the reduction of NAD(+), which is the rate-limiting step in the biosynthesis of guanine nucleotides. IMPDH is a promising target for chemotherapy. Microbial IMPDHs differ from mammalian enzymes in their lower affinity for inhibitors such as mycophenolic acid (MPA) and thiazole-4-carboxamide adenine dinucleotide (TAD). Part of this resistance is determined by the coupling between nicotinamide and adenosine subsites in the NAD(+) binding site that is postulated to involve an active site flap. To understand the structural basis of the drug selectivity, we solved the X-ray crystal structure of the catalytic core domain of Tritrichomonas foetus IMPDH in complex with IMP and beta-methylene-TAD at 2.2 A resolution. Unlike previous structures of this enzyme, the active site loop is ordered in this complex, and the catalytic Cys319 is 3.6 A from IMP, in the same plane as the hypoxanthine ring. The active site loop forms hydrogen bonds to the carboxamide of beta-Me-TAD which suggests that NAD(+) promotes the nucleophillic attack of Cys319 on IMP. The interactions of the adenosine end of TAD are very different from those in the human enzyme, suggesting the NAD(+) site may be an exploitable target for the design of antimicrobial drugs. In addition, a new K(+) site is observed at the subunit interface. This site is adjacent to beta-Me-TAD, consistent with the link between the K(+) activation and NAD(+). However, contrary to the coupling model, the flap does not cover the adenosine subsite and remains largely disordered.
| | The line below this paragraph, {{ABSTRACT_PUBMED_12403633}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12403633 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12403633}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Flexible loop]] | | [[Category: Flexible loop]] |
| [[Category: Ternary complex]] | | [[Category: Ternary complex]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 00:13:24 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jul 2 21:54:40 2008'' |
