Description

Plastocyanin-like domain :
This family is a plant-specific phytocyanins which constitute a distinct subfamily related to the copper binding protein plastocyanin. The family can be 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 [PUBMED:9761472, PUBMED:11085657, PUBMED:15858169, PUBMED:15631465]. Early nodulins lack amino acid residues that coordinate Cu, so they are believed to be involved in unknown processes without binding Cu [PUBMED: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 [PUBMED:9761472, PUBMED:11085657, PUBMED:15858169, PUBMED:15631465]
Copper binding proteins, plastocyanin/azurin family
Plastocyanin/azurin family of copper-binding proteins (or blue (type 1) copper domain) is a family of small proteins that bind a single copper atom. The most well-known members of this class of proteins are the plant chloroplastic plastocyanins, which exchange electrons with cytochrome c6, and the distantly related bacterial azurins, which exchange electrons with cytochrome c551.
Multicopper oxidase (Ascorbate oxidase and Laccase)
They oxidise their substrate by accepting electrons at a mononuclear copper centre and transferring them to a trinuclear copper centre; dioxygen binds to the trinuclear centre and, following the transfer of four electrons, is reduced to two molecules of water