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Mol. Biol. Cell 21 (3): 489-498

Copyright © 2010 by The American Society for Cell Biology.


The β Subunit of the Heterotrimeric G Protein Triggers the Kluyveromyces lactis Pheromone Response Pathway in the Absence of the {gamma} Subunit

Rocío Navarro-Olmos*, Laura Kawasaki*, Lenin Domínguez-Ramírez{dagger}, Laura Ongay-Larios*, Rosario Pérez-Molina*, and Roberto Coria*

*Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and {dagger}Department of Molecular and Cellular Biology, College of Biological Sciences, University of California at Davis, Davis, CA 95616

Received for publication June 10, 2009. Revision received November 24, 2009. Accepted for publication December 2, 2009.

Monitoring Editor: Charles Boone

Abstract: The Kluyveromyces lactis heterotrimeric G protein is a canonical Gαβ{gamma} complex; however, in contrast to Saccharomyces cerevisiae, where the G{gamma} subunit is essential for mating, disruption of the KlG{gamma} gene yielded cells with almost intact mating capacity. Expression of a nonfarnesylated G{gamma}, which behaves as a dominant-negative in S. cerevisiae, did not affect mating in wild-type and {Delta}G{gamma} cells of K. lactis. In contrast to the moderate sterility shown by the single {Delta}KlGα, the double {Delta}KlGα {Delta}KlG{gamma} mutant displayed full sterility. A partial sterile phenotype of the {Delta}KlG{gamma} mutant was obtained in conditions where the KlGβ subunit interacted defectively with the Gα subunit. The addition of a CCAAX motif to the C-end of KlGβ, partially suppressed the lack of both KlGα and KlG{gamma} subunits. In cells lacking KlG{gamma}, the KlGβ subunit cofractionated with KlGα in the plasma membrane, but in the {Delta}KlGα {Delta}KlG{gamma} strain was located in the cytosol. When the KlGβ-KlGα interaction was affected in the {Delta}KlG{gamma} mutant, most KlGβ fractionated to the cytosol. In contrast to the generic model of G-protein function, the Gβ subunit of K. lactis has the capacity to attach to the membrane and to activate mating effectors in absence of the G{gamma} subunit.

This article was published online ahead of print in MBC in Press ( on December 16, 2009.

Address correspondence to: Dr. Roberto Coria (rcoria{at}

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