Alternative ligands as probes for the carotenoid-binding site of lobster carapace crustacyanin.

The apoproteins of the lobster carotenoprotein, crustacyanin, show single high-affinity binding sites for the hydrophobic fluorescence probes 8-anilo-1-naphthalenesulphonic acid and cis-parinaric acid, and exhibit fluorescence transfer from tryptophan to the ligands. These results, together with information from the amino acid sequences, infer that the native carotenoid, astaxanthin, is bound to each apoprotein within an internal hydrophobic pocket, or calyx.