Copper, azurin proteins

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

Direct evidence for long range electron-transfer in biological systems was first observed by Gray et al.50,51) and Isied et al.481 using [Ru(NH3)5]3+ substituted metallo protein. Histidine-83 of blue copper (azurin) was labeled with Ru(III)(NH3)5 50). Flash photolysis reduction of the His-83 bound Ru(III) followed by electron-transfer from the Ru(II) to Cu2+ was observed with a rate constant of 1.9 s 1. The result shows that intramolecular long distance (approx. 1 nm) electron-transfer from the Ru(II) to the Cu2 + of the azurin takes place rapidly. 

Brill, A. S. Conformational distribution and vibronic coupling in the blue copper-containing protein azurin, in Tunneling in biological systems (eds. Chance, B. et al.) p. 561, New York, Academic Press 1979... 

Figure 7-16. Structure of azurin. Protein secondary structure is represented by P-strands (ribbons with arrows) and a single a-helix (represented by a coil). The amino acid side chains coordinating the copper ion and those of the two cysteine residues forming a disulfide bond are also shown. Reprinted from ref. 53 with permission.

Copper Blue Proteins.— The present understanding of the chemistry of the copper blue electron-transfer proteins has taken a significant step forward with the publication of molecular structures for azurin and plastocyanin. ... 

Azurin a family of blue, copper-containing proteins from Pseudcmumas, Alcattgenes and Bordetelia species. A. from Pseudorrumas fluorescens contains 128 amino add residues of known sequence, and one intrachain disulfide bond. A. from all sources has M, 14,000-16,000 and homologous primary and tertiary structure, but different spedes of A. have different redox potentials. 

Structural studies on electron transfer metalloproteins provide an important origin for discussion of the electron transfer processes themselves.The reduction potentials of a number of cytochromes c, cyt c copper blue proteins plastocyanin, Pc azurin, Az stellacyanin, St and HiPIP, or high potential iron protein, from Chromatium vinosum have been determined using spectro-... 

Type 1.5 and type 2 copper-cysteinate proteins do not exist in nature they have all been constructed by site directed mutagenesis on different proteins, mainly azurin or Cu,Zn-superoxide dismutase. For the type 1.5 proteins, a recent crystal structure is available, the azide derivative of the Met 121-Ala azurin mutant. In addition, preliminary results on the Metl21-His azurin mutant, another type 1.5 protein, have also been presented. ... 

In the blue, Type I copper proteins plastocyanin and azurin, the active-site structure comprises the trigonal array [CuN2S] of two histidine ligands and one cysteine ligand about the copper,... 

It is interesting to speculate why nitrite reductase has its type I coppers in domains 1, whereas in hCP the mononuclear copper binding sites are retained in the domains 2,4, and 6 where they are comparatively buried in the protein. One possible reason can be related to the difference in functions of the two proteins. NR has to interact with a relatively large pseudo-azurin macromolecule in order for electron transfer to take place,... 

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