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| {{STRUCTURE_2cf5| PDB=2cf5 | SCENE= }} | | {{STRUCTURE_2cf5| PDB=2cf5 | SCENE= }} |
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| '''CRYSTAL STRUCTURES OF THE ARABIDOPSIS CINNAMYL ALCOHOL DEHYDROGENASES, ATCAD5'''
| | ===CRYSTAL STRUCTURES OF THE ARABIDOPSIS CINNAMYL ALCOHOL DEHYDROGENASES, ATCAD5=== |
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| ==Overview==
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| The cinnamyl alcohol dehydrogenase (CAD) multigene family in planta encodes proteins catalyzing the reductions of various phenylpropenyl aldehyde derivatives in a substrate versatile manner, and whose metabolic products are the precursors of structural lignins, health-related lignans, and various other metabolites. In Arabidopsis thaliana, the two isoforms, AtCAD5 and AtCAD4, are the catalytically most active being viewed as mainly involved in the formation of guaiacyl/syringyl lignins. In this study, we determined the crystal structures of AtCAD5 in the apo-form and as a binary complex with NADP+, respectively, and modeled that of AtCAD4. Both AtCAD5 and AtCAD4 are dimers with two zinc ions per subunit and belong to the Zn-dependent medium chain dehydrogenase/reductase (MDR) superfamily, on the basis of their overall 2-domain structures and distribution of secondary structural elements. The catalytic Zn2+ ions in both enzymes are tetrahedrally coordinated, but differ from those in horse liver alcohol dehydrogenase since the carboxyl side-chain of Glu70 is ligated to Zn2+ instead of water. Using AtCAD5, site-directed mutagenesis of Glu70 to alanine resulted in loss of catalytic activity, thereby indicating that perturbation of the Zn2+ coordination was sufficient to abolish catalytic activity. The substrate-binding pockets of both AtCAD5 and AtCAD4 were also examined, and found to be significantly different and smaller compared to that of a putative aspen sinapyl alcohol dehydrogenase (SAD) and a putative yeast CAD. While the physiological roles of the aspen SAD and the yeast CAD are uncertain, they nevertheless have a high similarity in the overall 3D structures to AtCAD5 and 4. With the bona fide CAD's from various species, nine out of the twelve residues which constitute the proposed substrate-binding pocket were, however, conserved. This is provisionally considered as indicative of a characteristic fingerprint for the CAD family. | | The line below this paragraph, {{ABSTRACT_PUBMED_16633561}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16633561 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16633561}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Oxidoreductase]] | | [[Category: Oxidoreductase]] |
| [[Category: Zinc]] | | [[Category: Zinc]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 21:58:57 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 10:40:17 2008'' |
