Structure of the Active Site

FIGURE 8.1. The structure of the active site of SNase with a bound inhibitor that is used as a model for the substrate. 

We have illustrated in detail the efforts made in the last few decades to discover the structure of the active sites of the Philhps catalyst and to solve the mystery of the initiation step, which is unique among the polymerization catalysts because it proceeds without activators. From the survey of the hterature it can be safely concluded that much progress has been achieved in the understanding of the surface structure and catalytic activity of the Cr/Si02 system. In particular, concerning the surface structure, the following points now appear to be firmly estabhshed ... 

Fig. 1. Structure of the active site of H0I as determined by x-ray crystallography (41). Broken lines are used to designate hydrogen bonding of the water molecule to Glu 114 and Glu 243, as well as the semibridging interaction of Glu 144 with the diiron center.

Figure 2-8. (A) X-ray structure of GPx dimer, (B) monomer used as die real system in ONIOM calculations, and (C) structure of the active site including two water molecules (Adapted from Prabhakar et al. [27]. Reprinted with permission. Copyright 2004 American Chemical Society.)...

STRUCTURE OF THE ACTIVE SITE IN MYOGLOBIN AND HEMOGLOBIN COMPARISON TO MODEL COMPOUNDS... 

The hydrogenation catalysts can be prepared in situ, starting from the surface alkyl complex. In terms of catalytic performances, these catalysts are highly effective (Table 6.21) [150]. The best hydrogenation systems are based on silica supported dinuclear complexes, for which the structures of the active sites have not been investigated. Hydrogenation of toluene and xylenes can be achieved under similar conditions. 

It is also of interest to point out that the amino acid sequence and structure of the active site of vanadium haloperoxidases is conserved within several families of phosphatases, with conservation of the amino acids involved in vanadate binding in one and phosphate binding in the other. 

The molecular structure of the active site of the monooxygenase isolated from Methylococcus capsulatus is shown in Figure l.1... 

Figure 31 X-Ray structure of the active site of Fe-protein in the nitrogenase of Azotobacter vinelandii. Polypeptide chains surround the central Fe4S4 cluster...

Figure 16 X-Ray structure of the active site of cytochrome P450cam. In the camphor-bound form the bond distances are Fe-S 2.20 A Fe-N 2.05 A.33 The heme geometry of the camphor-free form is substantially similar to that of the camphor-bound form the only difference is that the iron atom is displaced from the tetrapyrrole plane towards the axial sulfur atom by 0.30 A in the camphor-free form, and by 0.44 A in the camphor-bound form...

Figure 25 X-Ray structure of the active sites of the 4Fe proteins (a) HiPIP Chromatium vinosum (b) Bacillus thermoproteolyticus...

---