title: Low-resolution molecular structures of isolated functional units from arthropodan and molluscan hemocyanin.
abstract: Synchrotron x-ray scattering measurements were performed on dilute solutions of the purified hemocyanin subunit (Bsin1) from scorpion (Buthus sindicus) and the N-terminal functional unit (Rta) from a marine snail (Rapana thomasiana). The model-independent approach based on spherical harmonics was applied to calculate the molecular envelopes directly from the scattering profiles. Their molecular shapes in solution could be restored at 2-nm resolution. We show that these units represent stable, globular building blocks of the two hemocyanin families and emphasize their conformational differences on a subunit level. Because no crystallographic or electron microscopy data are available for isolated functional units, this study provides for the first time structural information for isolated, monomeric functional subunits from both hemocyanin families. This has been made possible through the use of low protein concentrations (< or = 1 mg/ml). The observed structural differences may offer advantages in building very different overall molecular architectures of hemocyanin by the two phyla.
authors.affiliation: CCLRC Daresbury Laboratory, Warrington, Cheshire WA4 4AD, England.
authors.forename: J G
authors.initials: JG
authors.lastname: Grossmann
authors.forename: S A
authors.initials: SA
authors.lastname: Ali
authors.forename: A
authors.initials: A
authors.lastname: Abbasi
authors.forename: Z H
authors.initials: ZH
authors.lastname: Zaidi
authors.forename: S
authors.initials: S
authors.lastname: Stoeva
authors.forename: W
authors.initials: W
authors.lastname: Voelter
authors.forename: S S
authors.initials: SS
authors.lastname: Hasnain
mesh_terms: D000818:Animals; D006433:Hemocyanins / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D012542:Scattering, Radiation; D012605:Scorpions / Q000737:chemistry; D012908:Snails / Q000737:chemistry; D017356:Synchrotrons; D014965:X-Rays
chemical_list: D006433:Hemocyanins