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Mol Cell Biol

Title:		Biochemical and genetic analysis of dominant-negative mutations affecting a yeast G-protein gamma subunit
Author(s):		Grishin AV; Weiner JL; Blumer KJ;
Address:		"Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110"
Journal Title:		Mol Cell Biol
Year:		1994
Volume:		14
Issue:		7
Page Number:		4571 - 4578
DOI:		10.1128/mcb.14.7.4571-4578.1994
ISSN/ISBN:		0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking)
Abstract:		"Heterotrimeric guanine nucleotide-binding proteins (G proteins) consisting of alpha, beta, and gamma subunits mediate signalling between cell surface receptors and intracellular effectors in eukaryotic cells. To define signalling functions of G gamma subunits (STE18 gene product) involved in pheromone response and mating in the yeast Saccharomyces cerevisiae, we isolated and characterized dominant-negative STE18 alleles. We obtained dominant-negative mutations that disrupt C-terminal sequences required for prenylation of G gamma precursors (CAAX box) and that affect residues in the N-terminal half of Ste18p. Overexpression of mutant G gamma subunits in wild-type cells blocked signal transduction; this effect was suppressed upon overexpression of G beta subunits. Mutant G gamma subunits may therefore sequester G beta subunits into nonproductive G beta gamma dimers. Because mutant G gamma subunits blocked the constitutive signal resulting from disruption of the G alpha subunit gene (GPA1), they are defective in functions required for downstream signalling. Ste18p bearing a C107Y substitution in the CAAX box displayed reduced electrophoretic mobility, consistent with a prenylation defect. G gamma subunits carrying N-terminal substitutions had normal electrophoretic mobilities, suggesting that these proteins were prenylated. G gamma subunits bearing substitutions in their N-terminal region or C-terminal CAAX box (C107Y) supported receptor-G protein coupling in vitro, whereas C-terminal truncations caused partial defects in receptor coupling"
Keywords:		"Alleles Amino Acid Sequence *GTP-Binding Protein gamma Subunits GTP-Binding Proteins/biosynthesis/*genetics Gene Expression/drug effects *Genes, Dominant *Genes, Fungal *Heterotrimeric GTP-Binding Proteins Kinetics Macromolecular Substances Molecular Sequ;"
Notes:		"MedlineGrishin, A V Weiner, J L Blumer, K J eng GM44592/GM/NIGMS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 1994/07/01 Mol Cell Biol. 1994 Jul; 14(7):4571-8. doi: 10.1128/mcb.14.7.4571-4578.1994"