Phytocyanin domain (IPR003245)

Short name: Phytocyanin_dom

Overlapping homologous superfamilies

Domain relationships


Among the blue copper proteins with a single type I (or "blue") mononuclear copper site, the plant-specific phytocyanins constitute a distinct subfamily that can be further subdivided into the families of uclacyanins, stellacyanins, plantacyanins, and early nodulins. Stellacyanins have a blue copper coordinated by two His, one Cys and one Gln. In plantacyanins and uclacyanins, the ligands of the type-I Cu sites are two His, one Cys and one Met [PMID: 9761472, PMID: 11085657, PMID: 15858169, PMID: 15631465]. Early nodulins lack amino acid residues that coordinate Cu, so they are believed to be involved in unknown processes without binding Cu [PMID: 19897921]. Phytocyanins are found in chloropasts of higher plants.

The phytocyanin domain has a core of seven polypeptide strands arranged as a beta-sandwich comprising two beta-sheets, beta-sheet I and beta-sheet II. Beta-sheet I consists of three beta-strands and beta-sheet II consists of four beta-strands. A disulfide bridge close the metal centre is characteristic for phytocyanins, in contrast to azurins, pseudoazurins, and plastocyanins, where a disulfide bond is located on the distal side of the beta-barrel. This disuldide bridge may play a crucial role in maintaining the tertiary structure of the protein and/or the formation of the copper binding centre because one of the His ligands of copper is followed directly by a bridging Cys residue [PMID: 9761472, PMID: 11085657, PMID: 15858169, PMID: 15631465]. Some members of this family (P93328) may not bind copper due to the lack of key residues.

Some proteins known to contain a phytocyanin domain are listed below:

  • Cucumber basic protein (CBP).
  • Spinach basic protein (SBP).
  • Cucumber stellacyanin (CST).
  • Zucchini mavicyanin.
  • Horseradish umecyanin [PMID: 5089608, PMID: 11945593].

Some of the proteins in this family are allergens. The allergens in this family include allergens with the following designations: Amb a 3.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

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.
PROSITE profiles