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Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and molluscs. Comparison of the amino acid sequence data for seven different subunits of arthropod hemocyanins from crustaceans and chelicerates shows many highly conserved residues and extensive regions of near identity. This correspondence can be matched closely with the three domain structure established by x-ray crystallography for spiny lobster hemocyanin. The degree of identity is particularly striking in the second domain of the subunit that contains the six histidines which ligate the two oxygen-binding copper atoms. The polypeptide architecture of spiny lobster hemocyanin appears to be the same in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, about 540 to 600 million years ago.

The structure of hevamine shows a completely new lysozyme/chitinase fold and represents a new class of polysaccharide-hydrolyzing (beta alpha)8-barrel enzymes. Because the residues conserved in the family to which hevamine belongs are important for maintaining the structure of the (beta alpha)8-barrel, all members of the family, including fungal, bacterial and insect chitinases, are likely to share this architecture. The crystal structure obtained provides a basis for protein engineering studies in this family of chitinases.