2glx
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(New page: 200px<br /><applet load="2glx" size="350" color="white" frame="true" align="right" spinBox="true" caption="2glx, resolution 2.200Å" /> '''Crystal Structure A...)
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Revision as of 18:02, 29 January 2008
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Crystal Structure Analysis of bacterial 1,5-AF Reductase
Overview
Recombinant 1,5-anhydro-d-fructose reductase (AFR) from Sinorhizobium, morelense S-30.7.5 was crystallized in complex with the cofactor NADP(H), and its structure determined to 2.2 A resolution using selenomethionine, SAD (refined R(work) and R(free) factors of 18.9 and 25.0%, respectively)., As predicted from the sequence and shown by the structure, AFR can be, assigned to the GFO/IDH/MocA protein family. AFR consists of two domains., The N-terminal domain displays a Rossmann fold and contains the cofactor, binding site. The intact crystals contain the oxidized cofactor NADP(+), whose attachment to the cofactor binding site is similar to that of, NADP(+) in glucose-fructose oxidoreductase (GFOR) from Zymomonas mobilis., Due to variations in length and sequence within loop regions L3 and L5, respectively, the adenine moiety of NADP(+) adopts a different orientation, in AFR caused by residue Arg38 forming hydrogen bonds with the, 2'-phosphate moiety of NADP(+) and cation-pi stacking interactions with, the adenine ring. Amino acid replacements in AFR (S10G, A13G, and S33D), showed that Ala13 is crucial for the discrimination between NADPH and NADH, and yielded the A13G variant with dual cosubstrate specificity. The, C-terminal domain contains the putative substrate binding site that was, occupied by an acetate ion. As determined by analogy to GFOR and by, site-directed mutagenesis of K94G, D176A, and H180A, residues Lys94, Asp176, and His180 are most likely involved in substrate binding and, catalysis, as substitution of any of these residues resulted in a, significant decrease in k(cat) for 1,5-AF. In this context, His180 might, serve as a general acid-base catalyst by polarizing the carbonyl function, of 1,5-AF to enable the transfer of the hydride from NADPH to the, substrate. Here we present the first structure of an AFR enzyme catalyzing, the stereoselective reduction of 1,5-AF to 1,5-anhydro-d-mannitol, the, final step of a modified anhydrofructose pathway in S. morelense S-30.7.5., We also emphasize the importance of the A13G variant in biocatalysis for, the synthesis of 1,5-AM and related derivatives.
About this Structure
2GLX is a Single protein structure of sequence from Ensifer adhaerens with and as ligands. Active as 1,5-anhydro-D-fructose reductase, with EC number 1.1.1.263 Full crystallographic information is available from OCA.
Reference
Crystal structure of NADP(H)-dependent 1,5-anhydro-D-fructose reductase from Sinorhizobium morelense at 2.2 A resolution: construction of a NADH-accepting mutant and its application in rare sugar synthesis., Dambe TR, Kuhn AM, Brossette T, Giffhorn F, Scheidig AJ, Biochemistry. 2006 Aug 22;45(33):10030-42. PMID:16906761
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