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Mol Cell Biol

Title:		The C terminus of the Saccharomyces cerevisiae alpha-factor receptor contributes to the formation of preactivation complexes with its cognate G protein
Author(s):		Dosil M; Schandel KA; Gupta E; Jenness DD; Konopka JB;
Address:		"Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, New York 11794-5222, USA"
Journal Title:		Mol Cell Biol
Year:		2000
Volume:		20
Issue:		14
Page Number:		5321 - 5329
DOI:		10.1128/MCB.20.14.5321-5329.2000
ISSN/ISBN:		0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking)
Abstract:		"Binding of the alpha-factor pheromone to its G-protein-coupled receptor (encoded by STE2) activates the mating pathway in MATa yeast cells. To investigate whether specific interactions between the receptor and the G protein occur prior to ligand binding, we analyzed dominant-negative mutant receptors that compete with wild-type receptors for G proteins, and we analyzed the ability of receptors to suppress the constitutive signaling activity of mutant Galpha subunits in an alpha-factor-independent manner. Although the amino acid substitution L236H in the third intracellular loop of the receptor impairs G-protein activation, this substitution had no influence on the ability of the dominant-negative receptors to sequester G proteins or on the ability of receptors to suppress the GPA1-A345T mutant Galpha subunit. In contrast, removal of the cytoplasmic C-terminal domain of the receptor eliminated both of these activities even though the C-terminal domain is unnecessary for G-protein activation. Moreover, the alpha-factor-independent signaling activity of ste2-P258L mutant receptors was inhibited by the coexpression of wild-type receptors but not by coexpression of truncated receptors lacking the C-terminal domain. Deletion analysis suggested that the distal half of the C-terminal domain is critical for sequestration of G proteins. The C-terminal domain was also found to influence the affinity of the receptor for alpha-factor in cells lacking G proteins. These results suggest that the C-terminal cytoplasmic domain of the alpha-factor receptor, in addition to its role in receptor downregulation, promotes the formation of receptor-G-protein preactivation complexes"
Keywords:		"Alleles Amino Acid Substitution Cytoplasm/metabolism *GTP-Binding Protein alpha Subunits GTP-Binding Protein alpha Subunits, Gq-G11 GTP-Binding Proteins/genetics/*metabolism Genes, Dominant Genes, Lethal Heterotrimeric GTP-Binding Proteins/genetics/metabo;"
Notes:		"MedlineDosil, M Schandel, K A Gupta, E Jenness, D D Konopka, J B eng R01 GM034719/GM/NIGMS NIH HHS/ R01 GM055107/GM/NIGMS NIH HHS/ GM34719/GM/NIGMS NIH HHS/ GM55107/GM/NIGMS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 2000/06/24 Mol Cell Biol. 2000 Jul; 20(14):5321-9. doi: 10.1128/MCB.20.14.5321-5329.2000"