Higher order assemblies of molluscan hemocyanins

1. The hemocyanins of the Fissurellidae, Naticidae and Melongenidae families of marine gastropods as well as some other molluscs including some members of the Opistobranchia and Bivalvia groups have hemocyanins which exist in solution as tri-decameric and mixed, multi-decameric aggregates characterized by sedimentation coefficients close to 100 S, 130 S, 150 S, 170 S and 200 S to 230 S. 2. The particle masses of the molluscan hemocyanins appear to be integral multiples close to 4.4 x 10(6) daltons. Thus, particle mass values of 4.47 x 10(6), 8.67 x 10(6) and 13.40 x 10(6) daltons were obtained for representative decameric, di-decameric, and tri-decameric components of Stenoplax conspicua, Fasciolaria tulipa and Euspira (Lunatia) heros hemocyanins. For Busycon contrarium, a gastropod with a mixed multidecameric hemocyanin, scanning transmission electron microscopic (STEM) measurements gave particle masses ranging from 8.89 x 10(6) and 13.20 x 10(6) for the di- and tri-decameric components to 38.87 x 10(6) and 43.40 x 10(6) daltons for highest nano- and deca-decameric aggregates. 3. The electron microscopic images of both uranyl acetate-stained and unstained specimens of hemocyanin aggregates indicate a non-random mode of assembly of the multi-decameric particles. This is most apparent from the electron micrographs of the moon snail hemocyanins. The tri-decameric and tetra-decameric particles seem to be assembled from a single di-decameric unit of the Mellema and Klug arrangement, with the collar ends facing outward, to which decameric units have been added from one or both ends, in a unidirectional tail-to-head to tail-to-collar manner. Consequently, all the aggregates including the higher, Melongenidae polymers have the appearance of closed cylinders terminating with the collar ends. 4. The radial distribution of the end-on views of the hemocyanin of the moon-snail Calinatioina oldroydii, show that the radial mass drops to zero at the center of the cylindrical particles consisting of one, two, or three decamers. This suggests that no caps are present at the ends of the hemocyanin particles which would inhibit or terminate their linear assembly. 5. The light-scattering behavior of B. contrarium and Marisa cornarietis hemocyanins examined as a function of increasing reagent concentration using the hydrophobic urea and Hofmeister salt series of reagents, show distinct aggregation and increase in molecular weights at low concentrations of reagent. Together with the stabilizing influence of Mg2+ and Ca2+ ions, this suggests polar and ionic stabilization of the inter-decameric contacts between the central di-decamers and the added decameric units of the higher aggregates of molluscan hemocyanins.(ABSTRACT TRUNCATED AT 400 WORDS)