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Xiang BS , Markham GD
The conformation of inosine 5'-monophosphate (IMP) bound to IMP dehydrogenase determined by transferred nuclear Overhauser effect spectroscopy
Journal of Biological Chemistry. 1996 Nov 1;271(44) :27531-27535
PMID: ISI:A1996VQ67900056   
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IMP dehydrogenase (IMPDH) catalyzes the NAD-dependent synthesis of xanthosine 5'-monophosphate which is the rate-limiting step in guanine nucleotide biosynthesis. Although IMPDH is the target of numerous chemotherapeutic agents, nothing has been known about the conformation of the enzyme-bound substrates. The conformation of IMP bound to human type II IMP dehydrogenase has been determined by two-dimensional transferred nuclear Overhauser effect NMR spectroscopy at 600 MHz. NOE buildup rates were determined by recording NOESY spectra at numerous mixing times. The cross-relaxation rates determined from the initial NOE build-up rates were used to calculate interproton distances of bound IMP. The conformation of the enzyme-bound IMP was obtained by molecular modeling with energy minimization using the experimentally determined inter- proton distance constraints. The glycosidic torsion angle of the bound nucleotide is anti and the sugar is in the C-2-endo- conformation. This conformation places H-2 of IMP, which is transferred to NAD in the reaction, in a position clear of the rest of the molecule in order to facilitate the reaction.
Times Cited: 4 English Article VQ679 J BIOL CHEM