[Cloning preprolactin cDNA from Pacific salmon in Escherichia coli]

Prolactin coding mRNA was shown to be a prevalent part of chum salmon (Oncorhynchus keta) pituitary poly(A)-RNA during the spawning period. Clone lambda gtPrk12 was selected from the pituitary cDNA library by means of hybridization with the prolactin probe, and a nucleotide sequence of the insertion was determined and compared to the prolactin coding sequences from rainbow trout and Pacific chinook salmon, which had been published earlier. The sequences compared exhibited a significant homology. The deduced amino acid sequence of the chum salmon prolactin differed from a sequence determined directly in a single position. The prolactin-coding sequence can be used for constructing the bacterial strain producing prolactin.