The association of carotenoids with protein in certain invertebrates

Abstract

Crustacyanin, the blue carotenoprotein of the lobster carapace was obtained in a state homogeneous in cellulose acetate electrophoresis. It was crystallised and shown to be a globulin of large particle size, free from lipid and carbohydrate. The minimum molecular weight of the protein calculated on the carotenoid content, was found to be one-tenth of that expected from its size. Reversible changes in spectrum occurring on removal of salt were shown to be attended by dissociation into subunit of the size expected from the minimum molecular weight. Apocrustacyanin was shown to be of the subunit size and heterogeneous in cellulose acetate electrophoresis. Native cnustacyanin was reconstituted from the apoprotein and astaxanthin. Possible modes of binding of the carotenoid are suggested to account for the spectral changes occurring in urea. Electrophoretic similarities between crustacyanin treated with urea and apocrustacyanin are discussed in relation to the number of different subunits. It is suggested that crustacyanin is composed of a specific geometrical association of several small subunits, possibly different, and that the carotenoid stabilises the subunits in a configuration essential for the association and possibly also assisting in the binding. Ovoverdin, the green carotenoprotain of lobster ovary, was obtained homogeneous in cellulose acetate electrophoresis and shown to be a glycolipoprotein, precipitating at low ionic strength out soluble in distilled water. The possibility of two molecules of carotenoid being associated with each molecule of protein has been investigated. Astaxanthin-proteins were purified from the carapaces of Eriphia spinifrons, Carcinus maenas, Astacus astacus and Palinurus vulgaris. Their absorption spectra and properties arc compared with those of crustacyanin and ovoverdin. Glycolipoproteins containing a number of carotenoids have been purified from the ovaries of Carcinus maenas, Pecten maximus and Palinurus vulgaris, and from the eggs of Palinurns vulgaris. Their properties have been investigated and the ode of association of the carotenoids is discussed.