1d4f
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| , resolution 2.8Å | |||||||
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| Ligands: | and | ||||||
| Activity: | Adenosylhomocysteinase, with EC number 3.3.1.1 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
CRYSTAL STRUCTURE OF RECOMBINANT RAT-LIVER D244E MUTANT S-ADENOSYLHOMOCYSTEINE HYDROLASE
OverviewOverview
A site-directed mutagenesis, D244E, of S-adenosylhomocysteine hydrolase (AdoHcyase) changes drastically the nature of the protein, especially the NAD(+) binding affinity. The mutant enzyme contained NADH rather than NAD(+) (Gomi, T., Takata, Y., Date, T., Fujioka, M., Aksamit, R. R., Backlund, P. S., and Cantoni, G. L. (1990) J. Biol. Chem. 265, 16102-16107). In contrast to the site-directed mutagenesis study, the crystal structures of human and rat AdoHcyase recently determined have shown that the carboxyl group of Asp-244 points in a direction opposite to the bound NAD molecule and does not participate in any hydrogen bonds with the NAD molecule. To explain the discrepancy between the mutagenesis study and the x-ray studies, we have determined the crystal structure of the recombinant rat-liver D244E mutant enzyme to 2.8-A resolution. The D244E mutation changes the enzyme structure from the open to the closed conformation by means of a approximately 17 degrees rotation of the individual catalytic domains around the molecular hinge sections. The D244E mutation shifts the catalytic reaction from a reversible to an irreversible fashion. The large affinity difference between NAD(+) and NADH is mainly due to the enzyme conformation, but not to the binding-site geometry; an NAD(+) in the open conformation is readily released from the enzyme, whereas an NADH in the closed conformation is trapped and cannot leave the enzyme. A catalytic mechanism of AdoHcyase has been proposed on the basis of the crystal structures of the wild-type and D244E enzymes.
About this StructureAbout this Structure
1D4F is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.
ReferenceReference
Effects of site-directed mutagenesis on structure and function of recombinant rat liver S-adenosylhomocysteine hydrolase. Crystal structure of D244E mutant enzyme., Komoto J, Huang Y, Gomi T, Ogawa H, Takata Y, Fujioka M, Takusagawa F, J Biol Chem. 2000 Oct 13;275(41):32147-56. PMID:10913437
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