The goal of this research is to elucidate the structure- function relationships involved in the interaction between the pituitary hormone prolactin and its cellular receptor. Escherichia coli cells have been engineered to synthesize bovine methionyl-protactin. The bacterially-produced hormone is fully active in the Nb2 cell bioassay for lactogenic hormones. Comparison of the published amino acid sequences of ten lactogenic hormones aligned so as to maximize homology reveals that there are approximately 30 sites at which the same amino acid is conserved. Bovine growth hormone, which is not a lactogenic hormone, and is inactive in the Nb2 cell bioassay, has a different amino acid present at only six of these sites. In this study site directed mutagenesis techniques will be used to introduce specific amino acid changes at these six positions. Mutant hormones will be isolated, and their bioactivities analyzed. Prolactin is an important hormone excreted by the anterior pituitary gland. It regulates growth and development of the mammary gland and is essential for the production of milk. The results of this research will provide useful information on how prolactin functions at the molecular level.
