Blue or 'type-1' copper proteins are small proteins which bind a single
copper atom and which are characterized by an intense electronic absorption
band near 600 nm [1,2]. 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. This family of proteins also includes all the
proteins listed below (references are only provided for recently determined
Amicyanin from bacteria such as Methylobacterium extorquens or Thiobacillus
versutus that can grow on methylamine. Amicyanin appears to be an electron
receptor for methylamine dehydrogenase.
Auracyanins A and B from Chloroflexus aurantiacus . These proteins can
donate electrons to cytochrome c-554.
Cusacyanin (basic blue protein; plantacyanin, CBP) from cucumber.
Halocyanin from Natrobacterium pharaonis , a membrane associated copper-
Pseudoazurin from Pseudomonas.
Rusticyanin from Thiobacillus ferrooxidans. Rusticyanin is an electron
carrier from cytochrome c-552 to the a-type oxidase .
Stellacyanin from the Japanese lacquer tree.
Umecyanin from horseradish roots.
Allergen Ra3 from ragweed. This pollen protein is evolutionary related to
the above proteins, but seems to have lost the ability to bind copper.
Although there is an appreciable amount of divergence in the sequence of all
these proteins, the copper ligand sites are conserved and we have developed a
pattern which includes two of the ligands: a cysteine and a histidine.
In position 5 of the pattern, only the Alcaligenes protein has a Val;
all other proteins have either Phe or Tyr. In position 9 only CPC has Gly,
all others have Pro.
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