A highly conserved red pigment-concentrating hormone precursor in the blue crab Callinectes sapidus

A cDNA library was established from the eyestalk ganglia of the blue crab Callinectes sapidus. One clone was isolated (644 bp excluding the poly(A) tail) which encodes the red pigment-concentrating hormone (RPCH)-precursor, consisting of the 25 amino acid residue signal peptide, the RPCH, and a 73 amino acid residue RPCH-precursor related peptide. This clone displays high sequence similarity with a clone isolated from an eyestalk cDNA library of the shore crab Carcinus maenas, in accordance with the close phylogenetic relationship between these species. Northern blot experiments indicated the presence of two different mRNA transcripts which hybridized with a specific RPCH-cDNA probe pointing to the possibility of multiple RPCH isoforms in the blue crab. Although crustacean RPCH and the insect adipokinetic hormones (AKH) are structurally related, their precursors show little similarity.