Histidine superoxide dismutase ligand

Fig. 6.8. H NMR spectra of C112C02 (A) [28] and Cu2Ni2 (B) [29] superoxide dismutase. The dashed lines relate signals belonging to the various histidine ligands of the copper domain. The black-shaded signals disappear when the spectra are recorded in D2O.

The imidazole-bridge dimetallic centre in copper-zinc superoxide dismutase (EC 1.15.1.1) was a novel structural feature that had not previously been encountered in coordination chemistry [151], The Cu(II) ion is co-ordinated by four histidine side chains, His44, His46, His 118 and His61, and there is evidence for a fifth axial water ligand. 

From One Type 2 Copper Protein to Another Type 2 Copper Protein. It has been shown that a type 2 copper protein called copper-zinc superoxide dismutase (CuZnSOD) (Figure 15b) shares the same overall scaffold as its copper chaperone protein called copper chaperone for SOD (CCS). All of e zinc site ligands and three of four copper site histidine ligands in CuZnSOD are conserved in human CCS (hCCS). The zinc site in hCCS displayed the same structure as in CuZnSOD. The fourth ligand in the copper site of CuZnSOD is replaced by an aspartate residue in hCCS. Although aspartate could... 

Type 2 copper centers are not uniform in ligand or ligand stereochemistries. One common feature is, however, that in the active enzyme, one coordination site is always free to bind oxygen. The most common ligand in type 2 copper centers is histidine. Tyrosine (often modified), methionine, and cysteine occur as well. There are three histidines and a modified tyrosine in amine oxidase and lysyl oxidase [28]. In diamine oxidase, two of the histidine residues have probably been replaced by cysteines [29]. In galactose oxidase, the copper ion is coordinated by two tyrosines, two histidines and an acetate ion [30]. Dopamine-/J-hydroxylase contains two differently coordinated copper ions per functional unit. One is coordinated by three histidines and a methionine and the other by two histidines and another, yet unknown, ligand [ 31 ]. Last but not least, the type 2 copper ion in Cu,Zn-superoxide dismutase is coordinated by four histidine residues, one of which connects the copper ion to the zinc ion, the second metal ion in the active site of the enzyme [32,33] (Fig. 6). 

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