Structural comparison of cephalopod hemocyanins: phylogenetic significance.
Hemocyanins, the respiratory molecules of cephalopod mollusks, are hollow cylinders with five internal arches. Three hemocyanins representative of three orders of cephalopods (Benthoctopus species, Octopoda; Vampyroteuthis infernalis, Vampyromorpha; Sepia officinalis, Sepioidea) were subjected to cryoelectron microscopy and three-dimensional (3D) reconstruction. The structure of Benthoctopus hemocyanin, solved at 26.4-A resolution, possesses arches comprising two identical functional units. The similarity between these functional units and the structure recently observed in X-ray crystallography for Octopus by Cuff et al. (J. Mol. Biol., 1998, 232, 522-529) allows the identification of their N- and C-terminal domains in the 3D reconstruction volume. Conversely, arches present in the 3D reconstruction volume of Sepia hemocyanin (21.8 A resolution) contain four functional units that are disposed differently. The strong resemblance between the reconstruction volumes of Vampyroteuthis (21.4-A resolution) and Benthoctopus hemocyanins suggests that Sepioidea diverged from a group containing Octopoda and Vampyromorpha.
Mouche
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Laboratoire des Protéines Complexes, Université François Rabelais, Campus Médecine, 2 bis Boulevard Tonnellé, Tours Cedex, F-37032, France.
Boisset
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N
Lamy
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J
Zal
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Lamy
J N
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D000818:Animals; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D049832:Decapodiformes / Q000145:classification / Q000235:genetics; D006433:Hemocyanins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D008974:Mollusca / Q000145:classification / Q000235:genetics*; D049831:Octopodiformes / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D011487:Protein Conformation
D006433:Hemocyanins