title: The haemocyanin of the whelk, Busycon contrarium (Conrad): aggregation states and subunit structure.
abstract: 1. The haemocyanin of the left-handed whelk Busycon contrarium (Conrad) exists largely as six or more multi-decameric aggregates characterized by sedimentation coefficients of approximately 105S, 132S, 155S, 170S, 185S and about 200-220S. 2. These aggregates represent di- to hepta- or octa-decameric assemblies of the basic haemocyanin decamer having a mol. wt of 4.3 x 10(6)-4.5 x 10(6). 3. The fully dissociated subunits in 8.0 M urea (pH 8.5) and at pH 11.1, 0.01 M EDTA have mol. wts of 4.78 x 10(5) and 4.62 x 10(5), close to one-tenth of the mol. wt of the basic decameric unit of most gastropod haemocyanins. 4. The pH dependence of the mol. wts (Mw), studied by light-scattering at the constant protein concentration of 0.010%, exhibit bell-shaped pH transition profiles with mol. wt values of about 16 x 10(6) in the presence of 0.01 M Mg2+, in the pH region from about pH 4.5-8.0; in the absence of stabilizing divalent ions the observed mol. wt is about 10 x 10(6) at pH 4.5-7.0. Below pH 4.5 and above 7.0-8.0 there is a sharp drop in mol. wt to about 4 x 10(5)-4.5 x 10(5). 5. The transition profiles observed with both the urea and salt series of probes investigated at concentration = 0.010% are found to produce aggregation at low reagent concentrations with mol. wt changes from about 9 x 10(6)-12 x 10(6)-14 x 10(6), followed by a decrease in mol. wt below 4.3 x 10(6)-4.5 x 10(6) of the haemocyanin decamers.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Chemistry, Fordham University, Bronx, NY 10458.
authors.forename: T T
authors.initials: TT
authors.lastname: Herskovits
authors.forename: A E
authors.initials: AE
authors.lastname: Guzman
authors.forename: M G
authors.initials: MG
authors.lastname: Hamilton
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D002942:Circular Dichroism; D006433:Hemocyanins / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D008970:Molecular Weight; D011487:Protein Conformation / Q000187:drug effects; D012492:Salts / Q000494:pharmacology; D012908:Snails / Q000032:analysis*; D014508:Urea / Q000494:pharmacology; D014783:Viscosity
chemical_list: D002413:Cations, Divalent; D012492:Salts; D014508:Urea; D006433:Hemocyanins