The BioGRID | PUBLICATION VIEW

	Jun (2007); 0:
The RACK1 ortholog Asc1 functions as a G protein beta subunit coupled to glucose responsiveness in yeast-
Zeller CE, Parnell SC, Dohlman HG
Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260-
Abstract: According to the prevailing paradigm, G proteins are composed of three subunits, an a subunit with GTPase activity and a tightly associated ss subunit complex- In the yeast Saccharomyces cerevisiae there are two known Ga proteins -Gpa1 and Gpa2- but only one Gss, which binds only to Gpa1- Here we show that the yeast ortholog of RACK1 -receptor for activated C-kinase 1- Asc1 functions as the Gss for Gpa2- As with other known Gss proteins, Asc1 has a 7-WD domain structure, interacts directly with the Ga in a guanine nucleotide-dependent manner, and inhibits Ga guanine nucleotide exchange activity- In addition, Asc1 binds to the effector enzyme adenylyl cyclase -Cyr1-, and diminishes the production of cAMP in response to glucose stimulation- Thus while Gpa2 promotes glucose signaling through elevated production of cAMP, Asc1 has opposing effects on these same processes- Our findings reveal the existence of an unusual Gss subunit, one having multiple functions within the cell in addition to serving as a signal transducer for cell surface receptors and intracellular effectors-
[PUBMED: 17591772]