title: Solution structures of 2×6-meric and 4×6-meric hemocyanins of crustaceans Carcinus aestuarii, Squilla mantis and Upogebia pusilla.
abstract: Arthropod hemocyanins (Hcs) are a family of large, high molecular mass, extracellular oxygen transport proteins. They form oligomeric quaternary structures based on different arrangements of a basic 6×75 kDa hexameric unit. Their complex quaternary structures present binding sites for allosteric effectors and regulate the oxygen binding process in a cooperative manner. In order to describe the functional regulation of arthropod Hcs, a detailed description of their quaternary structure is necessary. We have utilized small angle X-ray scattering to characterize the structure of three arthropod Hcs in unperturbed conditions. Two different levels of complexity are evaluated: for the 2×6-meric case, we analyzed the Hcs of the portunid crab Carcinus aestuarii and stomatopod Squilla mantis, while in the case of 4×6-meric structures, we studied the Hc of the thalassinid shrimp Upogebia pusilla. While C. aestuarii Hc presented a structure comparable to other 2×6-meric crustacean Hcs, S. mantis Hc shows a peculiar and quite unique arrangement of its building blocks, resembling a substructure of giant Hcs found among cheliceratans. For U. pusilla, the arrangement of its subunits is described as tetrahedral, in contrast to the more common square planar 4×6-meric structure found in other arthropod Hcs.
authors.affiliation: Department of Biology, University of Padova, via Ugo Bassi 58/B, I-35131 Padova, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Mičetić
authors.forename: Carmen
authors.initials: C
authors.lastname: Losasso
authors.forename: Paolo Di
authors.initials: PD
authors.lastname: Muro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Tognon
authors.forename: Piero
authors.initials: P
authors.lastname: Benedetti
authors.forename: Mariano
authors.initials: M
authors.lastname: Beltramini
mesh_terms: D000818:Animals; D001665:Binding Sites; D003445:Crustacea / Q000378:metabolism; D006433:Hemocyanins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D020836:Protein Structure, Quaternary; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D006433:Hemocyanins; D010100:Oxygen