Small blue copper proteins including pseudocyanin, plastocyanin, halocyanin and amicyanin
The Pseudocyanin-like family of copper-binding proteins (or blue (type 1) copper domain) is a family of small proteins that bind a single copper atom and are characterized by an intense electronic absorption band near 600 nm. Pseudoazurin (PAz) has been identified as a electron donor in the denitrification pathway. For example, PAz acts as an electron donor to cytochrome c peroxidase and N2OR from Paracoccus pantotrophus (Pp), and to the copper containing nitrite reductase (NiR) that catalyzes the second step of denitrification. Plastocyanin is found in cyanobacteria, higher plants, and some algae where it plays a role in photosynthesis. Plastocyanin is responsible for transporting electrons from PSII to PSI. This family also includes halocyanins found in halophilic archaea such as Natronomonas pharaonis (Natronobacterium pharaonis) and amicyanin found in bacteria Paracoccus denitrificans.
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