Coenzyme surface orientation

A jx)ssible model to show the orientation of adsorbed coenzyme in its oxidized form on the electrode surface is schematically drawn in Fig. 38. CoQ would be adsorbed by means of its isoprenoid chain. By considering... 

The high resolution X-ray structural studies of the native enzyme, the enzyme-ADPR binary complex, and the enzyme-o-phenanthroline binary complex (47) have revealed that the active site zinc ion is located some 20 A below the surface of the protein at the point of convergence of two deep clefts (see the schematic representation in Fig. 6). One of these clefts has been identified as the coenzyme binding cleft (47). This cleft extends from the surface of the subunit to the zinc ion. If a model of NADH is fit to the coordinates of the ADPR binding site, then the nicotinamide ring can be oriented in such a way that it fits into a pocket adjacent to the zinc ion (47). The second deep cleft, or channel, also extends from the surface of the subunit down to the zinc ion. The inner surface of this cleft is made up of nonpolar amino acid residues contributed by both subunits. 

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