2cf5: Difference between revisions

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.

2CF5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Arabidopsis_thaliana Arabidopsis thaliana] with ZN as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Cinnamyl-alcohol_dehydrogenase Cinnamyl-alcohol dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.195 1.1.1.195] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2CF5 OCA].  

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