Ragweed allergen Ra3: relationship to some type 1 copper-binding proteins.

We have found ragweed allergen Ra3 to be related to the type 1 copper proteins; it is most closely related to stellacyanin and basic blue protein. The type 1 copper proteins form a diverse group of proteins, most of which are involved in electron transport. However, key amino acids believed to be involved in copper binding are absent from the allergen sequence; thus, the allergen is not likely to be functionally related to the type 1 copper proteins. We have grouped these proteins into one superfamily and we depict the relationships among them by an evolutionary tree. As indicated by this tree, an ancient gene duplication resulted in the divergence of plastocyanin from the line leading to basic blue protein, stellacyanin, and allergen Ra3.