Amicyanin/Pseudoazurin (IPR002386)

Short name: Amicyanin/Pseudoazurin

Overlapping homologous superfamilies

Family relationships


Based on their primary sequences and their unique metabolic role, amicyanins are considered as a distinct subclass of cupredoxins, although they appear to be closely related to the plant plastocyanins [PMID: 8035459].

The structure of amicyanin is a beta-sandwich, built from nine beta-strands. The copper atom is located between three loops on one end of the molecule. Two of these loops contribute the copper ligands. The other three ligands are located on the loop between strands 8 and 9. The structure departs from the general cupredoxin fold in having a 21-residue N-terminal extension, which forms an extra beta-strand, and it shows significant differences between strands 5 and 7 (this forms a helix in azurin and an acidic patch in plastocyanin).

Pseudoazurin, also called cupredoxin, is a small, blue periplasmic protein with a single bound copper atom. Pseudoazurin is related to plastocyanins [PMID: 8138527]. Several examples of pseudoazurin are encoded by a neighbouring gene for, or have been shown to transfer electrons to, copper-containing nitrite reductases (IPR001287) of the same species [PMID: 16138306].

Pseudoazurin has been identified as an electron donor to the denitrification pathway. For example, pseudoazurin acts as an electron donor to cytochrome c peroxidase and N2OR from Paracoccus pantotrophus [PMID: 22910335], and to the copper containing nitrite reductase that catalyzes the second step of denitrification [PMID: 15475344, PMID: 10364229]. It has been shown that pseudoazurin dramatically enhances the reaction profile of nitrite reduction by Paracoccus pantotrophus cytochrome cd1 and facilitates release of the product nitric oxide. The ability of this small redox protein to interact with a multitude of structurally different partners has been attributed to the hydrophobic character of the binding surface.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0005507 copper ion binding
GO:0009055 electron transfer activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.