A family of proteins known as cupredoxins contain a single redoxactive Cu ion coordinated by a Cys, a Met, and two His residues. The reduction potentials of cupredoxins range from about 0.15 V to 0.68 V. What does this information reveal about the role of the protein component of the cupredoxins?

A family of proteins known as cupredoxins contain a single redoxactive Cu ion coordinated by a Cys, a Met, and two His residues.

The reduction potentials of cupredoxins range from about 0.15 V to 0.68 V. This information reveals that the role of the protein component of the cupredoxins surpasses the maximum and minimun reduction potentials limits reported for any mononuclear cupredoxin, preserving the metal binding site furter than the typical values for the cupredoxin protein family.

Explanation:

These redox-active copper proteins´ structure and properties of native cupredoxins, and those modified by site-directed mutagenesis, although their wide range of E°, may have evolved to specifically bind copper, developed recognition sites for specific redox partners, tuned redox potential for a particular function, and allowed for efficient electron shuttle. The overall and active site structures are very similar in all T1 cupredoxins, 9 which contain a Cu ion coordinated by a Cys and two His residues in a trigonal planar geometry, and a weak axial ligand, such as Met121 in Az. This is basic to understand the roles of metals from energy metabolism, respiration, cell signaling, and photosynthesis, to catalysis in industrial and fuel cell research, as redox potentials are fine-tuned over a range with little change to the redox-active site or ET properties through a single redox active center, whose reduction potential (E°) must be tunable to match that of a given redox partner without compromising the structural and ET properties of the protein. A number of studies have shown that there is still a deep lack of knowledge about other long-range, non-covalent interactions responsible for tuning E°.