Novel antagonist to agonist switch in chimeric G protein-coupled alpha-factor peptide receptors

The alpha-factor analog desTrp1,Ala3 alpha-factor (dTA-alpha-factor) acts as an antagonist for both the S. cerevisiae alpha-factor receptor (c-alpha-FR) and the S. kluyveri alpha-factor receptor (k-alpha FR). Chimeric alpha-factor receptors in which a portion (residues 250-303) of the seven hydrophobic segments were derived from the k-alpha FR and the rest from c-alpha FR conferred potent activation of cellular responses by dTA-alpha-factor including induction of FUS1 expression without significantly affecting binding. Chimeric receptors with all hydrophobic segments derived from one receptor did not express sensitivity. We propose that dTA-alpha-factor represents an antagonist that that has an activation energy barrier to activating c-alpha FR and k-alpha FR but which retains a latent potential to act as an agonist.