Hemocyanins and Invertebrate Evolution

Kensal E Van Holde,Karen I Miller,Heinz Decker

doi:10.1074/jbc.r100010200

Kensal E Van Holde, Karen I Miller + Show 1 more

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https://doi.org/10.1074/jbc.r100010200

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Abstract

Hemocyanins and Invertebrate Evolution

Highlights

Each copper is ligated by three histidine residues, as shown in Fig. 1, and lies within a 4␣-helix bundle reminiscent of hemerythrin or perhaps even the globin fold [12]
In some other molluscs dimers or even higher oligomers of these decamers can be found. Such molecules are truly immense; the structure shown in Fig. 2C has a molecular mass of about 9 ϫ 106 Da and contains 160 oxygen-binding sites! Sequence analysis [13, 14] has revealed that the functional units within a molluscan hemocyanin monomer are quite similar, with 40 –50% identity
X-ray diffraction studies have shown that octopus hemocyanin [6], two arthropod hemocyanins [5, 12], and catechol oxidase [15] exhibit remarkable similarity in the spatial arrangement of the six histidine ligands that hold the copper atoms

Summary

Hemocyanins and Invertebrate Evolution*

From the ‡Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305 and ʈInstitute for Molecular Biophysics, University of Mainz, D55128 Mainz, Germany. This conservation lies in the three-dimensional structure rather than in the linear sequences. 18 and 19, for example), whereas the molluscan hemocyanins resemble more closely that group of enzymes known as tyrosinases [20] and catechol oxidases [15] Structural comparison of sweet potato catechol oxidase and the hemocyanin-binding domain from octopus reveals a specific similarity with respect to an unusual Cys-His thioether bridge, which holds one of the copper-binding histidines in the proper orientation The fact that both kinds of hemocyanins have weak phenol oxidase activity further supports the idea of close affinity [16, 17, 21, 22]. Just such a difference has been noted by comparing the crystal structure of sweet potato catechol oxidase with that of molluscan hemocyanin [15]

The Emergence of Hemocyanin Function

When Did Hemocyanins Originate?