Complete sequence and model for the A2 subunit of the carotenoid pigment complex, crustacyanin

Eur J Biochem. 1991 Apr 23;197(2):407-17. doi: 10.1111/j.1432-1033.1991.tb15925.x.


The complete sequence has been determined for the A2 subunit of crustacyanin, an astaxanthin-binding protein from the carapace of the lobster Homarus gammarus. The polypeptide chain is 174 residues long and is similar to proteins of the retinol-binding protein superfamily. Some regions of the sequence are most similar to the retinol-binding protein, beta-lactoglobulin subgroup, while the disulphide bonding pattern is more akin to that seen in the porphyrin binding proteins insecticyanin and bilin-binding protein. It is beginning to appear as though this superfamily of proteins, characterized by a similar gross structural framework, may be further subdivided into interrelated subclasses. Model building based on the coordinates of the known structure of human plasma retinol-binding protein and on empirical prediction algorithms has allowed the putative identification of side-chains which line the binding cavity. This pocket is larger than in retinol binding protein and beta-lactoglobulin but does not allow the carotenoid to adopt a folded conformation. The amino acid composition of the pocket does not support a 'charge-shift'-type hypothesis to support the bathochromic shift phenomenon which takes place on interaction of the chromophore with the protein. Instead aromatic side-chains may play a prominent role.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Carotenoids / genetics*
  • Carrier Proteins
  • Chromatography, Gel
  • Crustacea
  • Electrophoresis, Polyacrylamide Gel
  • Lactoglobulins / genetics
  • Molecular Sequence Data
  • Proteins / genetics*
  • Retinol-Binding Proteins / genetics
  • Retinol-Binding Proteins, Plasma
  • Sequence Alignment


  • Carrier Proteins
  • Lactoglobulins
  • Proteins
  • Retinol-Binding Proteins
  • Retinol-Binding Proteins, Plasma
  • crustacyanins
  • Carotenoids

Associated data

  • SWISSPROT/P80007