Azurin

Azurin is a blue copper-containing protein found in the bacterium Pseudomonas aeruginosa. It is a small, single-domain protein with a molecular weight of approximately 14 kDa. The blue color of azurin arises from a type 2 copper ion coordinated by two histidine residues and a cysteine residue. This copper ion is responsible for the protein's redox activity.

Azurin plays a role in the bacterial electron transport chain, transferring electrons from cytochrome c551 to cytochrome oxidase. This process is crucial for cellular respiration and energy production in Pseudomonas aeruginosa. The protein has been extensively studied due to its relatively simple structure and well-characterized redox properties.

The structure of azurin has been determined by X-ray crystallography and NMR spectroscopy. It consists of a beta-barrel fold, with the copper ion located in a hydrophobic pocket at the base of the barrel. The protein exhibits high thermodynamic stability and undergoes reversible reduction and oxidation of the copper ion.

Beyond its physiological role, azurin has also found applications in biosensing and bioelectrochemistry. Its ability to bind and transfer electrons makes it a potential component in electrochemical devices for detecting various analytes. The study of azurin has contributed significantly to our understanding of electron transfer mechanisms in biological systems and the properties of blue copper proteins.