1d4f
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(New page: 200px<br /><applet load="1d4f" size="450" color="white" frame="true" align="right" spinBox="true" caption="1d4f, resolution 2.8Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 10:53, 20 November 2007
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CRYSTAL STRUCTURE OF RECOMBINANT RAT-LIVER D244E MUTANT S-ADENOSYLHOMOCYSTEINE HYDROLASE
Overview
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 Structure
1D4F is a Single protein structure of sequence from Rattus norvegicus with NAD and ADN as ligands. Active as Adenosylhomocysteinase, with EC number 3.3.1.1 Full crystallographic information is available from OCA.
Reference
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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