The G? subunit signals through the Ste50 protein during the mating pheromone response in the yeast Kluyveromyces lactis.

ABSTRACT: Yeast mating signal transduction pathways require a heterotrimeric G protein composed of G?, G?, and G? subunits connected to a mitogen-activated protein kinase (MAPK) module. While in Saccharomyces cerevisiae elimination of G? induces constitutive activation of the mating pathway, in Kluyveromyces lactis it produces partial sterility, which indicates that K. lactis G? (KlG?) is required to positively activate mating. We use physical interaction experiments to determine that KlG? interacts with the adaptor protein KlSte50p. The Ras association (RA) domain of KlSte50p favored interaction with the GDP-bound KlG? subunit, and when the KlG? protein is constitutively activated, the interaction drops significantly. Additionally, KlSte50p strongly associates with the MAPK kinase kinase (MAPKKK) KlSte11p through its sterile alpha motif (SAM) domain. Genetic experiments placed KlSte50p downstream of the G protein ? subunit, indicating that KlG? may stimulate the mating pathway via KlSte50p. Fusion of KlSte50p to the KlG? subunit partially eliminated the requirement of KlG? for mating, indicating that one contribution of KlG? to the mating pathway is to facilitate plasma membrane anchoring of KlSte50p.

SUBMITTER: Sanchez-Paredes E 

PROVIDER: S-EPMC3127637 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature