The Rhodopsin-retinochrome system is essential for the visual photoreception of molluscs. cDNA coding for retinochrome of the squid (Todarodes pacificus) was cloned and the nucleotide sequence has been determined. The sequence (2.1 kb) covers the whole coding region of 903 bp. The deduced primary sequence suggests that retinochrome contains seven transmembrane spanning domains. The homology with bovine rhodopsin and the possible retinal binding site are also discussed.
