Protein copper containing

Many multiple copper containing proteins (e.g., laccase, ascorbate oxidase, hemo-cyanin, tyrosinase) contain so-called type III copper centers, which is a historical name (cf. Section 5.8 for type I and type II copper) for strongly exchange-coupled Cu(II) dimers. In sharp contrast to the ease with which 5=1 spectra from copper acetate are obtained, half a century of EPR studies on biological type III copper has not produced a single triplet spectrum. Why all type III centers have thus far remained EPR silent is not understood. 

H. Porter and S. Ainsworth, The isolation of the copper-containing protein cerebrocuprein I from normal human brain. J. Neurochem. 5, 91-98 (1959). 

The electrons subsequently pass to plastocyanin (PC), which is a copper-containing protein. The Cu-containing redox center of this 10.5 kD monomer cycles between Cu(I) and Cu(II) oxidation states. The structure of PC shows that... 

In copper and silver complexes, optimum ENDOR enhancements for all types of nuclei are usually achieved for tempeatures between 10 to 30 K. For Cu-ENDOR in copper containing proteins, temperatures 4K are sometimes required (see below). 

Since the first EPR work on Cu(II) ions in proteins in the late fifties193, a great many EPR investigations on copper-containing proteins have been reported194-198. For a classification of the copper proteins into type I (blue copper), type II (non-blue copper) and type III (binuclear cupric pair), the reader is referred to Fee197. ... 

As we will discuss later, in Chapter 8, free copper levels are extremely low within cells because the copper is bound to a family of metallochaperones, which are subsequently involved in the incorporation of copper into copper-containing proteins. The mechanism proposed for copper insertion into the Cu/Zn superoxide dismutase, SOD1, is presented in Figure 3.9. The copper chaperone, CCS, acquires copper as Cu+ from a copper transporter and then docks with the reduced dithiol form of SOD1 (Steps I and II) to give a docked... 

We will discuss in more detail in Chapter 8 how intracellular copper levels are maintained at extremely low levels by a series of copper chaperone proteins, which sequester newly assimilated copper within the cytoplasm of cells and deliver it in a targeted manner to be incorporated into specific copper-containing proteins. While copper uptake across the gastrointestinal tract is poorly understood—most probably utilising the divalent cation transporter... 

Contrary to popular belief, ceruloplasmin5, the principal copper-containing protein in plasma, ceruloplasmin, is not involved in copper transport. This is clearly underlined by the clinical observation that patients with aceruloplasminaemia (i.e. lacking ceruloplasmin in their blood) have perfectly normal copper metabolism and homeostasis. Copper is transported in plasma mostly by serum albumin with smaller amounts bound to low-molecular weight ligands like histidine. Likewise zinc is mostly transported in plasma bound to proteins (albumin and ot2-macroglobulin). 

In copper-containing proteins, three types of copper, classified on the basis of their visible, UV and EPR spectra, as originally proposed by one of the pioneers of copper biochemistry, Bo Malmstrom, are found. Types 1 and 2 have one copper atom, which has an intense blue colour in Type 1 and is almost colourless in Type 2 whereas Type 3 has an EPR-silent dicopper centre. More details of the three types are as follows ... 

The copper-binding sites in copper-containing proteins are characterized by three distinct classes. In Type-1, or blue copper centers, the copper is coordinated to at least two imidazole nitrogens from two histidyl residues and one sulfur from a cysteinyl residue. Type-1 coppers have small copper hyperfine couplings and a strong visible absorption in the Cu(ll) state. Type-2 or non-blue copper... 

Copper is the third most abundant trace element in humans, after iron and zinc (Underwood, 1977). It is critical to a variety of proteins with functions ranging from electron transfer to oxygen transport to active chemistry, such as insertion of oxygen in a substrate. Table I is a selected list of copper-containing proteins. 

Copper-containing protein Function Source Reference... 

Nitrite reductases and nitrous oxide reductases are relatively newly found copper-containing proteins involved in bacterial denitrification. N2O reductase may bear a relationship to cytochrome oxidase and, indeed, parallels it somewhat in function, being the terminal electron acceptor in its pathway. 

Recent publications signal the continued interest in the function of this protein. It has been called a stress enzyme, involved in influenza virus infection (Tomas and Toparceanu, 1986). An explanation for Wilson s disease in terms of a genetic defect resulting in failure to convert from a neonatal (i.e., low) level of ceruloplasmin and copper to a normal adult level has been reported (Srai et al., 1986). Tissue specificity for the binding of ceruloplasmin to membranes was demonstrated in a study investigating the possible role of ceruloplasmin-specific receptors in the transfer of copper from ceruloplasmin to other copper-containing proteins (Orena et al, 1986). Ceruloplasmin has been shown to be effective in transferring copper to Cu,Zn-SOD in culture (Dameron and Harris, 1987), as has copper albumin. In view of the variable content of copper in this protein, it is not clear which copper is transferred. 

The structural comparison of copper-containing proteins has provided a new dimension to the relationships suggested by sequence simi-... 

In the third chapter, Elinor T. Adman presents a comprehensive view of the structures of copper-containing proteins. This view includes the topological folding of many of these proteins, as shown by ribbon drawings, as well as details of copper-ligand interactions. 

Adsorption of azurin - a copper-containing protein on Au electrodes under physiological conditions - has been monitored at the molecular level, applying STM [304]. 

In 1847 E. Harless discovered the presence of copper in the blood of the octopus Eledone and the snail Helix pomatia (172, 173). Investigation of the phenomenon by which the blood and tissues of certain marine animals turn blue on exposure to air finally led to the discovery that the blood plasma of such animals contains copper combined with a protein. Because of its analogy to hemoglobin and its ability to carry oxygen, L. Fredericq in 1878 named the copper-containing protein in the blood of Octopus vulgaris hemocyanin (173, 174). 

A number of copper -containing protein compounds are enzymes with an oxidase function (ascorbic acid oxidase, urease, etc 1 and these play an important role in Ihe biological oxidation-reduction system. There is a definite relationship of copper with iron in connection with utilization of iron in hemoglobin function. 

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