Studies on a blue carotenoprotein, linckiacyanin, isolated from the starfish Linckia laevigata (Echinodermata: Asteroidea)

Abstract

1. 1. A blue carotenoprotein, linkiacyanin ( λ max 395 and 612 nm), has been isolated from the skin of the starfish Linckia laevigata, together with a yellow carotenoprotein ( λ max 402 nm; molecular size ca 0.5 × 10 3 kDa). 2. 2. Linckiacyanin has a large molecular size (> 10 3 kDa) with a predominant glycoprotein subunit of only 6 kDa. 3. 3. Two keto-carotenoids are present in the carotenoprotein: astaxanthin and the previously uncharacterized aromatic carotenoid, hydroxyclathriaxanthin. Zeaxanthin is also present. The minimum molecular weight estimate (16 kDa) implies at least 200 carotenoid molecules per linckiacyanin molecule. 4. 4. Linckiacyanin appears as discs (200–260 Å diameter) and spring-like structures in electron micrographs. 5. 5. Variation in the E 612 395 ratio for linkiacyanin preparations and polydispersity in molecular sieving is discussed in the light of circular dichroism and other studies. 6. 6. The properties of linckiacyanin are compared with those of other echinoderm and crustacean carotenoproteins.