Following the determination of the primary structures of the
apoprotein subunits of crustacyanin, and the identification of
significant homology between these sequences and those of
other lipid-binding proteins, notably human plasma retinolbinding
protein and fl-lactoglobulin, a model of the three-dimensional
structure of the dimer, fl-crustacyanin, was constructed
[12,13]. This model suggests that each subunit of the
dimer contains 4 fl-pleated sheets that form a fl-barrel, and the
astaxanthin molecule is positioned with one end in the apolar
interior of the barrel. The other end of the astaxanthin projects
out into the surrounding (aqueous) medium. When the two