Metalloproteins blue copper proteins

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

This discussion of copper-containing enzymes has focused on structure and function information for Type I blue copper proteins azurin and plastocyanin, Type III hemocyanin, and Type II superoxide dismutase s structure and mechanism of activity. Information on spectral properties for some metalloproteins and their model compounds has been included in Tables 5.2, 5.3, and 5.7. One model system for Type I copper proteins39 and one for Type II centers40 have been discussed. Many others can be found in the literature. A more complete discussion, including mechanistic detail, about hemocyanin and tyrosinase model systems has been included. Models for the blue copper oxidases laccase and ascorbate oxidases have not been discussed. Students are referred to the references listed in the reference section for discussion of some other model systems. Many more are to be found in literature searches.50... 

Electronic spectra of metalloproteins find their origins in (i) internal ligand absorption bands, such as n->n electronic transitions in porphyrins (ii) transitions associated entirely with metal orbitals (d-d transitions) (iii) charge-transfer bands between the ligand and the metal, such as the S ->Fe(II) and S ->Cu(II) charge-transfer bands seen in the optical spectra of Fe-S proteins and blue copper proteins, respectively. Figure 6.3a presents the characteristic spectrum of cytochrome c, one of the electron-transport haemoproteins of the mitochondrial... 

Blue copper proteins are a family of metalloproteins that have been found to play an important role in a number of electron-transfer reactions in nature. Solomon and coworkers have studied a range of blue copper enzymes in detail to produce a thorough description of how molecular and electronic structure interact to provide the function of these enzymes (26,158). 

The ability to exist in more than one oxidation state allows transition-metal complexes to serve as the active site of enzymes whose function is to transfer electrons (39). A great deal of effort has been directed at understanding the mechanisms of electron transfer in metalloproteins, such as cytochromes and blue copper proteins (40). Of particular interest is the mechanism by which an electron can tunnel from a metal center that is imbedded in a protein matrix to a site on the outer surface of the protein (7). A discussion of current theories is given in this volume. 

Metalloproteins that have been overexpressed may need to be reconstituted with their native metal(s). For example, overexpression of the blue copper protein azurin results in a mixture of apo- and Zn forms. When a gene of an uncharacterized metalloprotein is expressed, care must be taken to assure that the identity of the native metal is determined through studies of native protein. Overexpression of heme proteins typically requires reconstitution with hemin. In the case of c-type heme, the heme must be attached covalently to the polypeptide with the assistance of cellular machinery. Wide success in expressing a range of c-heme containing proteins has been achieved by expression of both the structural cytochrome gene and the apparatus for protein maturation. ... 

Metalloproteins, where the active site includes one or more metals, represent a very different class of proteins than those discussed above. The particular kinds of metalloproteins discussed here are those where the metal is redox active and represents a functional and not structural component of the system. Many mechanistic studies of metalloproteins have been carried out using radiation chemistry in the past 50 years. Two different ways of using radiation chemistry to query mechanisms will be illustrated here. The first, as described in the earliest of these studies using blue copper proteins such as azurin, involves using pulse radiolysis to change an oxidation state and thus... 

Figure 2.12 Overview of three-dimensional structures and in situ STM images of metalloproteins representative of the three ET protein classes characterized by single-crystal PFV and in situ STM to single-molecule resolution, (a) Blue copper protein P. aeruginosa azurin (PDB 4AZU) [94] ...

Small Redox Metalloproteins Blue Copper, Heme, and Iron-Sulfur Proteins... 

Adman, E. T. Structure and function of small blue copper proteins. In Topics in Molecular and Structural Biology Metalloproteins Harrison, P., Ed. MacMillan New York, 1985 Vol. 1, pp 1 2. 

One of the important roles of metalloproteins is electron transport between functional molecules in biological systems [39], Copper proteins are involved in electron transfer, redox reactions and the transport and activation of dioxygen. They are classified into Types I, II and III, and eir properties are as follows Type I One copper is involved in one unit. The copper has a strong absorption around 600 nm and small hyperfine coupling constants in ESR. It is called Blue copper protein. 

The copper(II) atoms present in copper metalloproteins have been classified according to their spectroscopic properties. Type-1, as found in blue copper proteins such as... 

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