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Pheromone‐ and Rsp5‐Dependent Ubiquitinaton of G Beta Subunit Ste4 in Yeast
Author(s) -
Zhu Ming,
Torres Mathew,
Dohlman Henrik,
Wang Yuqi
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.lb212
Subject(s) - ubiquitin , ubiquitin ligase , microbiology and biotechnology , phosphorylation , protein subunit , mutant , saccharomyces cerevisiae , heterotrimeric g protein , f box protein , ubiquitin conjugating enzyme , mating of yeast , chemistry , biology , signal transduction , biochemistry , yeast , g protein , gene
Ste4 is the beta subunit of the heterotrimeric G proteins that mediates mating signaling in budding yeast Saccharomyces cerevisiae. In this study, we show that Ste4 undergoes ubiquitination and this was largely promoted by mating pheromone. Ubiquitination of Ste4 requires a loop region, composed of the residues from 310 to 346 and critical for Ste4 phosphorylation. Interestingly, Ste4 phosphorylation‐defective mutants fail to undergo ubiquitination in response to pheromone stimulation. We found that the residue K340 within the loop region serves as a primary ubiquitination site, since Ste4 K340R mutant significantly diminishes its ubiquitination in response to pheromone stimulation. In addition, our study also identified Rsp5 as an E3‐ligase mediating Ste4 ubiquitination. Ste4 ubiquitination is completely blocked in Rsp5‐disruptive mutant. Rsp5 physically interacts with Ste4 in vivo and is capable of catalyzing Ste4 ubiquitination in vitro. Altogether, our findings revealed the novel ubiquitination of the Gβ, Ste4, catalyzed by the E3 enzyme Rsp5 on K340. The ubiquitination‐defective mutants of Ste4 generated in this study would provide a powerful and specific tool for examing the functional consequences of Ste4 ubiquitination on mating signaling.