Combined Role of Two Tryptophane Residues of α-Factor Pheromone

摘要

Amide analogs of tridecapeptide α-factor (WHWLQLKPGQPMYCONH2) of Saccharomyces cerevisiae, in which Trp at position 1 and 3 were replaced with other residues, were synthesized to ascertain whether cooperative interactions between two Trp residues occurred upon binding with its receptor. Analogs containing Ala or Aib at position 3 of the peptide [Ala3]α-factor amide (2) and [Aib3]α-factor amide (5) exhibited greater decreases in bioactivity than analogs with same residue at position one [Ala1]α-factor amide (1) and [Aib1]α- factor amide (4), reflecting that Trp3 may plays more important role than Trp1 for agonist activity. Analogs containing Ala or Aib in both position one and three 3, 6 exhibited complete loss of bioactivity, emphasizing both the essential role and the combined role of two indole rings for triggering cell signaling. In contrast, double substituted analog with D-Trp in both positions 9 exhibited greater activity than single substituted analog with D-Trp 8 or deleted analog 7, reflecting the combined contribution of two tryptophane residues of α-factor ligand to activation of Ste2p through interaction with residue Tyr266 and importance of the proper parallel orientation of two indole rings for efficient triggering of signal G protein coupled activation. Among ten amide analogs, [Ala1,3]α-factor amide (3), [Aib1,3]α-factor amide (6), [D-Trp3]α-factor amide (8) and [des-Trp1,Phe3]α-factor amide (10) were found to have antagonistic activity. Analogs 3 and 6 showed greater antagonistic activity than analogs 8 and 10.