During sexual development ascomycete fungi produce two types of peptide pheromones termed a and α. The α pheromone from the budding yeast Saccharomyces cerevisiae, a 13-residue peptide that elicits cell cycle arrest and chemotropic growth, has served as paradigm for the interaction of small peptides with their cognate G protein-coupled receptors. However, no structural information is currently available for α pheromones from filamentous ascomycetes, which are significantly shorter and share almost no sequence similarity with the S. cerevisiae homolog. High resolution structure of synthetic α-pheromone from the plant pathogenic ascomycete Fusarium oxysporum revealed the presence of a central β-turn resembling that of its yeast counterpart. Disruption of the-fold by d-alanine substitution of the conserved central Gly⁶-Gln⁷ residues or by random sequence scrambling demonstrated a crucial role for this structural determinant in chemoattractant activity. Unexpectedly, the growth inhibitory effect of F. oxysporum α-pheromone was independent of the cognate G protein-coupled receptors Ste2 and of the central β-turn but instead required two conserved Trp¹-Cys² residues at the N terminus. These results indicate that, despite their reduced size, fungal α-pheromones contain discrete functional regions with a defined secondary structure that regulate diverse biological processes such as polarity reorientation and cell division.

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Journal Article

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Vitale S, Partida-Hanon A, Serrano S, Martínez-Del-Pozo Á, Di Pietro A, Turrà D, Bruix M

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