Structure-function studies of yeast mating pheromones

Mating in Saccharomyces cerevisiae is initiated by extracellular peptides, known as mating pheromones. The mating factors are recognized by membrane-bound receptors which are similar to receptors in mammalian cells. The pheromone system of the S. cerevisiae can be used as a model to understand the mode of action of peptide hormones in more complex mammalian system. The purpose of this thesis is to provide information regarding the yeast mating pheromones. The first part of this project, described in Chapter 2, was to characterize α-factor analogs with an inserted p- Benzoylphenylalanine (Bpa) residue. This residue is photoactivatable by UV light, and it has been inserted because studies have shown that photoaffinity labeling can be used for the identification and localization of receptors. By performing biological assays, an analog with activity mimicking that of wild type α-factor (Norleucine¹²) was identified. This analog can be used in future studies in attempts to elucidate the binding site of the α-factor with its receptor. The second phase of this thesis project was to develop an assay which could be used to define the binding of a-factor to its receptor. As described in Chapter 3, an efficient binding assay could not be developed due to the hydrophobicity of the a-factor pheromone; however results achieved from these experiments could be a starting point for future attempts to develop a successful binding assay.